diff --git a/.vscode/ios-sim-debug.sh b/.vscode/ios-sim-debug.sh
new file mode 100755
index 0000000..42291df
--- /dev/null
+++ b/.vscode/ios-sim-debug.sh
@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+# preLaunchTask for "Debug SxChess (iOS sim)": build SxChess for the iOS
+# simulator with debug info, install it to a single simulator, and launch it
+# PAUSED for a debugger (--wait-for-debugger). The launch.json `custom` config
+# then `target create`s the local binary (so the .dSYM resolves breakpoints)
+# and `process attach -n SxChess`es the waiting process.
+set -e
+
+SX="/Users/agra/projects/sx/zig-out/bin/sx"
+DSYMUTIL="/opt/homebrew/opt/llvm@19/bin/dsymutil"
+# Reuse ONE simulator (sx-test-ios18). Swap the UDID for a different device.
+SIM="E8DF755C-997D-49D7-9DB0-CFA48F8254CD"
+APP="sx-out/ios/M3te.app"
+BUNDLE="co.swipelab.m3te"
+
+# Debug build: -O0 + DWARF (--emit-obj keeps the object), then a portable .dSYM.
+"$SX" build --target ios-sim --emit-obj main.sx
+"$DSYMUTIL" "$APP/M3te"
+
+# Boot the sim (idempotent) and surface the Simulator UI.
+xcrun simctl boot "$SIM" 2>/dev/null || true
+xcrun simctl bootstatus "$SIM" >/dev/null 2>&1 || true
+open -a Simulator
+
+xcrun simctl install "$SIM" "$APP"
+xcrun simctl terminate "$SIM" "$BUNDLE" >/dev/null 2>&1 || true
+
+# Launch paused; the app waits at its entry until lldb attaches and continues.
+xcrun simctl launch --wait-for-debugger "$SIM" "$BUNDLE"
diff --git a/.vscode/launch.json b/.vscode/launch.json
new file mode 100644
index 0000000..050a629
--- /dev/null
+++ b/.vscode/launch.json
@@ -0,0 +1,27 @@
+{
+  "version": "0.2.0",
+  "configurations": [
+    {
+      "type": "lldb",
+      "request": "launch",
+      "name": "Debug M3te (macOS)",
+      "program": "${workspaceFolder}/sx-out/macos/M3te.app/Contents/MacOS/M3te",
+      "cwd": "${workspaceFolder}",
+      "preLaunchTask": "sx build (macos debug)"
+    },
+    {
+      "type": "lldb",
+      "request": "custom",
+      "name": "Debug M3te (iOS sim)",
+      "preLaunchTask": "sx build+launch (ios-sim debug)",
+      "targetCreateCommands": [
+        "target create '${workspaceFolder}/sx-out/ios/M3te.app/M3te'"
+      ],
+      "processCreateCommands": [
+        "process attach -n M3te",
+        "process handle SIGSTOP --notify false --stop false --pass false",
+        "process continue"
+      ]
+    }
+  ]
+}
diff --git a/.vscode/tasks.json b/.vscode/tasks.json
new file mode 100644
index 0000000..327015b
--- /dev/null
+++ b/.vscode/tasks.json
@@ -0,0 +1,23 @@
+{
+  "version": "2.0.0",
+  "tasks": [
+    {
+      "label": "sx build (macos debug)",
+      "detail": "Build M3te for macOS with DWARF (-O0) and collect a .dSYM for lldb.",
+      "type": "shell",
+      "command": "/Users/agra/projects/sx/zig-out/bin/sx build --target macos --emit-obj main.sx && /opt/homebrew/opt/llvm@19/bin/dsymutil sx-out/macos/M3te.app/Contents/MacOS/M3te",
+      "options": { "cwd": "${workspaceFolder}" },
+      "group": "build",
+      "problemMatcher": []
+    },
+    {
+      "label": "sx build+launch (ios-sim debug)",
+      "detail": "Build for the iOS simulator (-O0 + .dSYM), install, and launch paused for the debugger.",
+      "type": "shell",
+      "command": "${workspaceFolder}/.vscode/ios-sim-debug.sh",
+      "options": { "cwd": "${workspaceFolder}" },
+      "group": "build",
+      "problemMatcher": []
+    }
+  ]
+}
diff --git a/audio.sx b/audio.sx
index 3e75b61..cca1698 100644
--- a/audio.sx
+++ b/audio.sx
@@ -15,12 +15,12 @@
 
 // AudioToolbox — System Sound Services. SystemSoundID is a UInt32; OSStatus a
 // SInt32 (0 == noErr); the clip's file is passed as a CFURLRef (opaque ptr).
-AudioServicesCreateSystemSoundID :: (url: *void, out_id: *u32) -> s32 #foreign;
+AudioServicesCreateSystemSoundID :: (url: *void, out_id: *u32) -> i32 #foreign;
 AudioServicesPlaySystemSound     :: (sound_id: u32) #foreign;
 
 // CoreFoundation — build a file CFURL from an absolute path. `len` is a CFIndex
 // (long); `is_dir` a Boolean (unsigned char); a NULL allocator = default.
-CFURLCreateFromFileSystemRepresentation :: (allocator: *void, buffer: *u8, len: s64, is_dir: s8) -> *void #foreign;
+CFURLCreateFromFileSystemRepresentation :: (allocator: *void, buffer: *u8, len: i64, is_dir: i8) -> *void #foreign;
 CFRelease :: (cf: *void) #foreign;
 
 // libc — getcwd to absolutize the bundle-relative asset path. The platform
@@ -80,7 +80,7 @@ GameAudio :: struct {
 
     // Pick the ascending cascade clip by clamping the cascade depth into the
     // combo1..combo5 range (see `cascade_cue_index`).
-    play_cascade :: (self: *GameAudio, depth: s64) {
+    play_cascade :: (self: *GameAudio, depth: i64) {
         inline if OS != .ios { return; }
         if !self.loaded { return; }
         idx := cascade_cue_index(depth);
@@ -107,7 +107,7 @@ GameAudio :: struct {
 // `log show` shows the clip stepping up with cascade depth. Literals only — the
 // string→NSString bridge needs NUL-terminated bytes (a formatted string may not
 // be). `idx` is a clamped `cascade_cue_index`, so it is always 0..COMBO_CLIPS-1.
-cascade_cue_name :: (idx: s64) -> string {
+cascade_cue_name :: (idx: i64) -> string {
     if idx <= 0 { return "[sx] audio: cue combo1"; }
     if idx == 1 { return "[sx] audio: cue combo2"; }
     if idx == 2 { return "[sx] audio: cue combo3"; }
@@ -118,7 +118,7 @@ cascade_cue_name :: (idx: s64) -> string {
 // Cascade depth (number of cleared rounds) → combo clip index 0..COMBO_CLIPS-1
 // (combo1..combo5). Clamps: depth <= 1 → 0, depth >= 5 → 4. Pure arithmetic and
 // OS-agnostic so it can be snapshot-tested headlessly (P10.4).
-cascade_cue_index :: (depth: s64) -> s64 {
+cascade_cue_index :: (depth: i64) -> i64 {
     if depth <= 1 { return 0; }
     if depth >= COMBO_CLIPS { return COMBO_CLIPS - 1; }
     depth - 1
@@ -145,7 +145,7 @@ load_system_sound :: (name: string) -> u32 {
     if getcwd(@cwd_buf[0], 1024) == null { return 0; }
     cwd : string = ---;
     cwd.ptr = @cwd_buf[0];
-    cwd.len = cast(s64) c_strlen(@cwd_buf[0]);
+    cwd.len = cast(i64) c_strlen(@cwd_buf[0]);
 
     // CFURLCreateFromFileSystemRepresentation takes an explicit byte length, so
     // the formatted path needs no NUL terminator.
@@ -169,6 +169,6 @@ g_audio : *GameAudio = null;
 
 sfx_swap    :: ()           { if g_audio != null { g_audio.play_swap(); } }
 sfx_match   :: ()           { if g_audio != null { g_audio.play_match(); } }
-sfx_cascade :: (depth: s64) { if g_audio != null { g_audio.play_cascade(depth); } }
+sfx_cascade :: (depth: i64) { if g_audio != null { g_audio.play_cascade(depth); } }
 sfx_win     :: ()           { if g_audio != null { g_audio.play_win(); } }
 sfx_lose    :: ()           { if g_audio != null { g_audio.play_lose(); } }
diff --git a/board.sx b/board.sx
index 36b2ea1..af6f4f7 100644
--- a/board.sx
+++ b/board.sx
@@ -39,36 +39,36 @@ EMPTY_CHAR :: 46;   // '.'
 
 gem_char :: (g: Gem) -> u8 {
     if g == .empty { return EMPTY_CHAR; }
-    GEM_CHARS[cast(s64) g]
+    GEM_CHARS[cast(i64) g]
 }
 
 // ── Deterministic RNG ─────────────────────────────────────────────────────
 // A 32-bit linear congruential generator (Numerical Recipes constants),
-// carried in an s64 and masked back to 32 bits after every step so the
+// carried in an i64 and masked back to 32 bits after every step so the
 // stream is identical regardless of host integer width. The state*MUL+ADD
-// product stays well under s64 range, so no intermediate overflow. Any seed
+// product stays well under i64 range, so no intermediate overflow. Any seed
 // (including 0) yields a valid stream — an LCG has no forbidden state.
 RNG_MASK32 :: 0xFFFFFFFF;
 RNG_MUL    :: 1664525;
 RNG_ADD    :: 1013904223;
 
 Rng :: struct {
-    state: s64;
+    state: i64;
 
     // Advance and return the next 32-bit value.
-    next_u32 :: (self: *Rng) -> s64 {
+    next_u32 :: (self: *Rng) -> i64 {
         self.state = (self.state * RNG_MUL + RNG_ADD) & RNG_MASK32;
         self.state
     }
 
     // Uniform-ish value in [0, n). Uses the high bits, whose period is far
     // longer than the low bits of an LCG.
-    next_range :: (self: *Rng, n: s64) -> s64 {
+    next_range :: (self: *Rng, n: i64) -> i64 {
         (self.next_u32() >> 16) % n
     }
 }
 
-rng_seeded :: (seed: s64) -> Rng {
+rng_seeded :: (seed: i64) -> Rng {
     Rng.{ state = seed & RNG_MASK32 }
 }
 
@@ -106,7 +106,7 @@ Board :: struct {
     // round's base points (see `score_round`), and `resolve` adds each cascade
     // round's base scaled by `combo_multiplier` (P3.2). The HUD (P4.4) reads this
     // field. A hand-built board must zero this before accumulating.
-    score: s64;
+    score: i64;
 
     // Turn accounting (P3.3). `moves_made` counts the swaps actually COMMITTED —
     // only a legal swap (one that resolved into >=1 match) via `commit_swap`
@@ -115,15 +115,15 @@ Board :: struct {
     // is derived from the two, so there is a single source of truth and the
     // counters can never drift apart. A hand-built board must set both before
     // committing swaps.
-    moves_made: s64;
-    move_limit: s64;
+    moves_made: i64;
+    move_limit: i64;
 
     // Per-level score goal (P7.1). `init` sets it to DEFAULT_TARGET_SCORE;
     // `level_status` reads it to decide a win (`score >= target_score`). A
     // hand-built board must set this before its status is read.
-    target_score: s64;
+    target_score: i64;
 
-    idx :: (col: s64, row: s64) -> s64 {
+    idx :: (col: i64, row: i64) -> i64 {
         row * BOARD_COLS + col
     }
 
@@ -131,15 +131,15 @@ Board :: struct {
     // to 0 when the budget is spent (and below it only if a caller keeps
     // committing past the budget — see DEFAULT_MOVE_LIMIT). The turn/goal loop
     // (P7) reads this to decide when the game ends.
-    moves_remaining :: (self: *Board) -> s64 {
+    moves_remaining :: (self: *Board) -> i64 {
         self.move_limit - self.moves_made
     }
 
-    at :: (self: *Board, col: s64, row: s64) -> Gem {
+    at :: (self: *Board, col: i64, row: i64) -> Gem {
         self.cells[Board.idx(col, row)]
     }
 
-    set :: (self: *Board, col: s64, row: s64, g: Gem) {
+    set :: (self: *Board, col: i64, row: i64, g: Gem) {
         self.cells[Board.idx(col, row)] = g;
     }
 
@@ -149,7 +149,7 @@ Board :: struct {
     // already-placed cells to its left or above is excluded, and the gem is
     // drawn from the remaining allowed types. At most two types are ever
     // excluded, so a choice always remains.
-    init :: (self: *Board, seed: s64) {
+    init :: (self: *Board, seed: i64) {
         self.rng = rng_seeded(seed);
         self.score = 0;
         self.moves_made = 0;
@@ -165,7 +165,7 @@ Board :: struct {
 
 // Choose a gem for (col, row) that can't extend an existing run leftward or
 // upward. Pure given the board's already-placed prefix and the RNG state.
-pick_gem :: (board: *Board, rng: *Rng, col: s64, row: s64) -> Gem {
+pick_gem :: (board: *Board, rng: *Rng, col: i64, row: i64) -> Gem {
     forbidden : [GEM_COUNT]bool = ---;
     for 0..GEM_COUNT (t) { forbidden[t] = false; }
 
@@ -173,14 +173,14 @@ pick_gem :: (board: *Board, rng: *Rng, col: s64, row: s64) -> Gem {
     if col >= 2 {
         left := board.at(col - 1, row);
         if left == board.at(col - 2, row) {
-            forbidden[cast(s64) left] = true;
+            forbidden[cast(i64) left] = true;
         }
     }
     // Two same gems immediately above → a third of that type matches.
     if row >= 2 {
         up := board.at(col, row - 1);
         if up == board.at(col, row - 2) {
-            forbidden[cast(s64) up] = true;
+            forbidden[cast(i64) up] = true;
         }
     }
 
@@ -223,12 +223,12 @@ board_dump :: (self: *Board) -> string {
 MatchMask :: struct {
     cells: [BOARD_CELLS]bool;
 
-    at :: (self: *MatchMask, col: s64, row: s64) -> bool {
+    at :: (self: *MatchMask, col: i64, row: i64) -> bool {
         self.cells[Board.idx(col, row)]
     }
 
-    count :: (self: *MatchMask) -> s64 {
-        n : s64 = 0;
+    count :: (self: *MatchMask) -> i64 {
+        n : i64 = 0;
         for 0..BOARD_CELLS (i) { if self.cells[i] { n += 1; } }
         n
     }
@@ -237,7 +237,7 @@ MatchMask :: struct {
 // Mark a closed span of cells along one axis. `vertical` picks the axis; `fixed`
 // is the constant coordinate (the row for a horizontal span, the column for a
 // vertical one) and the span covers `start..end` of the moving coordinate.
-mark_run :: (m: *MatchMask, vertical: bool, fixed: s64, start: s64, end: s64) {
+mark_run :: (m: *MatchMask, vertical: bool, fixed: i64, start: i64, end: i64) {
     for start..end (i) {
         if vertical {
             m.cells[Board.idx(fixed, i)] = true;
@@ -317,8 +317,8 @@ dump_matches :: (b: *Board, m: *MatchMask) -> string {
 // A board cell address. Kept separate from the row-major index so swap callers
 // and the move enumeration speak in (col, row) like the rest of the model.
 Cell :: struct {
-    col: s64;
-    row: s64;
+    col: i64;
+    row: i64;
 }
 
 // Exchange the gems of two cells, in place. `swap` is its own inverse: calling
@@ -413,8 +413,8 @@ dump_swaps :: (swaps: *List(Swap)) -> string {
 // unchanged. Returns the number of cells cleared. `mask` is the matched-cell SET
 // from find_matches, so overlapping L/T shapes (already unioned into a single
 // `true` per shared cell) clear as one set with no double-counting.
-clear_cells :: (board: *Board, mask: *MatchMask) -> s64 {
-    cleared : s64 = 0;
+clear_cells :: (board: *Board, mask: *MatchMask) -> i64 {
+    cleared : i64 = 0;
     for 0..BOARD_CELLS (i) {
         if mask.cells[i] {
             board.cells[i] = .empty;
@@ -428,7 +428,7 @@ clear_cells :: (board: *Board, mask: *MatchMask) -> s64 {
 // cells cleared — 0 when there are no matches, in which case the board is left
 // unchanged. The count drives later cascade/scoring (P2.2+): a non-zero result
 // means the board changed and the resolution loop should continue.
-clear_matches :: (board: *Board) -> s64 {
+clear_matches :: (board: *Board) -> i64 {
     m := find_matches(board);
     clear_cells(board, @m)
 }
@@ -489,9 +489,9 @@ collapse :: (board: *Board) -> bool {
 // only ever yields ordinals 0..GEM_COUNT, so a hole is never refilled with
 // `.empty`; afterwards the board has no holes left. Returns the number of cells
 // filled (0 on a board that had none).
-refill :: (board: *Board) -> s64 {
+refill :: (board: *Board) -> i64 {
     rng := @board.rng;
-    filled : s64 = 0;
+    filled : i64 = 0;
     for 0..BOARD_ROWS (row) {
         for 0..BOARD_COLS (col) {
             if board.at(col, row) == .empty {
@@ -526,11 +526,11 @@ refill :: (board: *Board) -> s64 {
 // make "did this settle clear a 4 / 5+ run" observable. `had_len4` /
 // `had_len5_plus` are the boolean view of the same counts.
 Cascade :: struct {
-    depth: s64;
-    cleared: List(s64);
-    awarded: s64;
-    len4: s64;
-    len5_plus: s64;
+    depth: i64;
+    cleared: List(i64);
+    awarded: i64;
+    len4: i64;
+    len5_plus: i64;
 
     had_len4 :: (self: *Cascade) -> bool {
         self.len4 > 0
@@ -546,7 +546,7 @@ Cascade :: struct {
 // number of cells cleared this round — 0 iff the board was already stable, in
 // which case nothing moves and no gem is drawn. `resolve` repeats this until it
 // returns 0.
-resolve_step :: (board: *Board) -> s64 {
+resolve_step :: (board: *Board) -> i64 {
     cleared := clear_matches(board);
     if cleared == 0 { return 0; }
     collapse(board);
@@ -560,7 +560,7 @@ resolve_step :: (board: *Board) -> s64 {
 // Each round adds `score_round * combo_multiplier(round)` (round 1-based) to
 // `Board.score`; an already-stable board returns depth 0, awards 0, untouched.
 resolve :: (board: *Board) -> Cascade {
-    result := Cascade.{ depth = 0, cleared = List(s64).{}, awarded = 0, len4 = 0, len5_plus = 0 };
+    result := Cascade.{ depth = 0, cleared = List(i64).{}, awarded = 0, len4 = 0, len5_plus = 0 };
     while true {
         // Read the round's base points AND its special-match tally while the runs
         // are still on the board: `resolve_step` clears them, so both have to be
@@ -604,15 +604,15 @@ SCORE_RUN_5_PLUS :: 100;
 // vertical one) and the run covers `start..start+len` of the moving coordinate.
 Run :: struct {
     vertical: bool;
-    fixed: s64;
-    start: s64;
-    len: s64;
+    fixed: i64;
+    start: i64;
+    len: i64;
 }
 
 // Base points for a single maximal run, by length. Runs are always length >= 3
 // (shorter spans are not enumerated), so 3 is the floor; 5 and longer all score
 // the top tier.
-run_score :: (len: s64) -> s64 {
+run_score :: (len: i64) -> i64 {
     if len <= 3 { return SCORE_RUN_3; }
     if len == 4 { return SCORE_RUN_4; }
     SCORE_RUN_5_PLUS
@@ -666,9 +666,9 @@ find_runs :: (b: *Board) -> List(Run) {
 // read-only — it inspects the board but changes nothing, so it must be called
 // BEFORE the round's clear, while the runs are still on the board. A board with
 // no run scores 0.
-score_round :: (board: *Board) -> s64 {
+score_round :: (board: *Board) -> i64 {
     runs := find_runs(board);
-    total : s64 = 0;
+    total : i64 = 0;
     for 0..runs.len (i) {
         total += run_score(runs.items[i].len);
     }
@@ -679,7 +679,7 @@ score_round :: (board: *Board) -> s64 {
 // `score` total and return them. The single-round accumulation primitive; the
 // cascade loop (`resolve`) instead scales each round by `combo_multiplier`
 // (P3.2). Neither path changes `score_round`.
-add_round_score :: (board: *Board) -> s64 {
+add_round_score :: (board: *Board) -> i64 {
     points := score_round(board);
     board.score += points;
     points
@@ -694,7 +694,7 @@ add_round_score :: (board: *Board) -> s64 {
 // multi-round chain strictly beats the same clears scored flat. `resolve`
 // accumulates `score_round * combo_multiplier(round)` per round into `Board.score`
 // and reports the sum as `Cascade.awarded`.
-combo_multiplier :: (round: s64) -> s64 {
+combo_multiplier :: (round: i64) -> i64 {
     round
 }
 
@@ -711,8 +711,8 @@ combo_multiplier :: (round: s64) -> s64 {
 // "did any occur" lives on `Cascade` (`had_len4` / `had_len5_plus`) for the
 // whole settle; a single round reads these counts directly.
 SpecialCounts :: struct {
-    len4: s64;
-    len5_plus: s64;
+    len4: i64;
+    len5_plus: i64;
 }
 
 // Count the board's currently-matched runs that hit a special length, by the
@@ -766,7 +766,7 @@ dump_runs :: (runs: *List(Run)) -> string {
 PlayerMove :: struct {
     legal: bool;
     cascade: Cascade;
-    moves_remaining: s64;
+    moves_remaining: i64;
 }
 
 // Attempt the player's intended swap of two adjacent cells. If the swap is legal
@@ -779,7 +779,7 @@ PlayerMove :: struct {
 // spent (that is the P7 turn-loop's call) — see DEFAULT_MOVE_LIMIT.
 commit_swap :: (board: *Board, a: Cell, b: Cell) -> PlayerMove {
     if !swap_legal(board, a, b) {
-        empty := Cascade.{ depth = 0, cleared = List(s64).{}, awarded = 0, len4 = 0, len5_plus = 0 };
+        empty := Cascade.{ depth = 0, cleared = List(i64).{}, awarded = 0, len4 = 0, len5_plus = 0 };
         return PlayerMove.{ legal = false, cascade = empty, moves_remaining = board.moves_remaining() };
     }
     swap(board, a, b);
@@ -900,7 +900,7 @@ reshuffle_if_deadlocked :: (board: *Board) -> bool {
 // seed → identical starting layout), zeroes `score` and `moves_made`, and
 // restores the default move budget and score goal, so `level_status` reads
 // `in_progress` again. The entry point P7.2's restart button calls.
-restart :: (board: *Board, seed: s64) {
+restart :: (board: *Board, seed: i64) {
     board.init(seed);
 }
 
@@ -930,7 +930,7 @@ TurnResult :: struct {
 play_turn :: (board: *Board, a: Cell, b: Cell) -> TurnResult {
     status := level_status(board);
     if status != .in_progress {
-        empty := Cascade.{ depth = 0, cleared = List(s64).{}, awarded = 0, len4 = 0, len5_plus = 0 };
+        empty := Cascade.{ depth = 0, cleared = List(i64).{}, awarded = 0, len4 = 0, len5_plus = 0 };
         frozen := PlayerMove.{ legal = false, cascade = empty, moves_remaining = board.moves_remaining() };
         return TurnResult.{ accepted = false, move = frozen, status = status, reshuffled = false };
     }
diff --git a/board_anim.sx b/board_anim.sx
index 9dc536f..a22ca61 100644
--- a/board_anim.sx
+++ b/board_anim.sx
@@ -109,7 +109,7 @@ bad_swap_bounce :: (t: f32) -> f32 {
 // ease_in_cubic so each column still accelerates under gravity within its window.
 // `tests/easing.sx` pins f(0)=0, f(1)=1, monotonicity, and the cascade ordering.
 FALL_STAGGER_MAX :f32: 0.30;
-fall_stagger_t :: (t: f32, col: s64) -> f32 {
+fall_stagger_t :: (t: f32, col: i64) -> f32 {
     delay := FALL_STAGGER_MAX * (cast(f32) col / cast(f32) (BOARD_COLS - 1));
     window := 1.0 - FALL_STAGGER_MAX;
     lt := (t - delay) / window;
@@ -123,7 +123,7 @@ fall_stagger_t :: (t: f32, col: s64) -> f32 {
 // at `1 - FALL_STAGGER_MAX`; the last column lands exactly at 1.0. The landing
 // squash-bounce (P17.3) ages from this instant per column, so the squash begins
 // the moment a gem touches its cell rather than at a flat whole-row settle.
-fall_landing_frac :: (col: s64) -> f32 {
+fall_landing_frac :: (col: i64) -> f32 {
     (1.0 - FALL_STAGGER_MAX) + FALL_STAGGER_MAX * (cast(f32) col / cast(f32) (BOARD_COLS - 1))
 }
 
@@ -132,7 +132,7 @@ fall_landing_frac :: (col: s64) -> f32 {
 // per-round bounce ages from. Round k's fall starts after the swap, k clear+fall
 // pairs, and that round's own clear; column `col` then lands `fall_landing_frac`
 // of the fall window into it. Pure + headless, mirrors `phase`'s segment walk.
-round_land_time :: (k: s64, col: s64) -> f32 {
+round_land_time :: (k: i64, col: i64) -> f32 {
     SWAP_ANIM_DUR + cast(f32) k * (CLEAR_ANIM_DUR + FALL_ANIM_DUR) + CLEAR_ANIM_DUR
         + fall_landing_frac(col) * FALL_ANIM_DUR
 }
@@ -159,10 +159,10 @@ clear_ripple_t :: (t: f32, u: f32) -> f32 {
 
 // The diagonal (col+row) extent of a round's matched cells — the span the ripple
 // ranks each matched gem across. `hi < lo` only if the mask is empty.
-ClearDiag :: struct { lo: s64; hi: s64; }
+ClearDiag :: struct { lo: i64; hi: i64; }
 clear_diag_span :: (m: *MatchMask) -> ClearDiag {
-    lo : s64 = (BOARD_COLS - 1) + (BOARD_ROWS - 1) + 1;
-    hi : s64 = -1;
+    lo : i64 = (BOARD_COLS - 1) + (BOARD_ROWS - 1) + 1;
+    hi : i64 = -1;
     for 0..BOARD_CELLS (i) {
         if m.cells[i] {
             d := (i % BOARD_COLS) + (i / BOARD_COLS);
@@ -178,7 +178,7 @@ clear_diag_span :: (m: *MatchMask) -> ClearDiag {
 // PER ROUND (not across the board) lets even a small 3-match ripple across the
 // full stagger budget. A degenerate span (every matched cell on one diagonal)
 // ranks all gems 0, so they pop together rather than dividing by zero.
-clear_rank :: (span: ClearDiag, col: s64, row: s64) -> f32 {
+clear_rank :: (span: ClearDiag, col: i64, row: i64) -> f32 {
     if span.hi <= span.lo { return 0.0; }
     cast(f32) ((col + row) - span.lo) / cast(f32) (span.hi - span.lo)
 }
@@ -193,7 +193,7 @@ clear_rank :: (span: ClearDiag, col: s64, row: s64) -> f32 {
 AnimRound :: struct {
     before: [BOARD_CELLS]Gem;
     matched: MatchMask;
-    src: [BOARD_CELLS]s64;
+    src: [BOARD_CELLS]i64;
     after: [BOARD_CELLS]Gem;
 }
 
@@ -210,7 +210,7 @@ AnimMove :: struct {
     pre: [BOARD_CELLS]Gem;
     rounds: List(AnimRound);
     final: [BOARD_CELLS]Gem;
-    awarded: s64;
+    awarded: i64;
 }
 
 // The most recent round at or before `kmax` that dropped a MOVED gem onto
@@ -221,7 +221,7 @@ AnimMove :: struct {
 // ages from its LATEST arrival, never a stale earlier one. Pure + headless: the
 // per-round bounce (render_fall/clear) and the final-settle stamp share this so
 // one envelope plays continuously across every seam.
-delivering_round :: (mv: *AnimMove, i: s64, kmax: s64) -> s64 {
+delivering_round :: (mv: *AnimMove, i: i64, kmax: i64) -> i64 {
     row := i / BOARD_COLS;
     k := kmax;
     while k >= 0 {
@@ -312,7 +312,7 @@ AnimPhaseKind :: enum { swap; clear; fall; done; }
 
 AnimPhase :: struct {
     kind: AnimPhaseKind;
-    round: s64;
+    round: i64;
     t: f32;
 }
 
@@ -327,7 +327,7 @@ BoardAnim :: struct {
     // so the frame loop's per-round SFX is edge-triggered: a round's cue fires once,
     // when its clear begins, never re-fired every frame. Reset whenever a move
     // (re)starts; advanced by the frame loop as rounds clear.
-    cascade_fired: s64;
+    cascade_fired: i64;
 
     init :: (self: *BoardAnim) {
         self.active = false;
@@ -383,11 +383,11 @@ BoardAnim :: struct {
 // have fired by now (clamped to the move's round count). The frame loop diffs it
 // against `BoardAnim.cascade_fired` to play one cue per newly-cleared round. Pure +
 // headless so the per-round playback is snapshot-testable without audio.
-cascade_rounds_started :: (elapsed: f32, num_rounds: s64) -> s64 {
+cascade_rounds_started :: (elapsed: f32, num_rounds: i64) -> i64 {
     if num_rounds <= 0 { return 0; }
     if elapsed < SWAP_ANIM_DUR { return 0; }
     seg := CLEAR_ANIM_DUR + FALL_ANIM_DUR;
-    started := cast(s64) ((elapsed - SWAP_ANIM_DUR) / seg) + 1;
+    started := cast(i64) ((elapsed - SWAP_ANIM_DUR) / seg) + 1;
     if started > num_rounds { return num_rounds; }
     started
 }
diff --git a/board_fx.sx b/board_fx.sx
index f055ab5..6d315f3 100644
--- a/board_fx.sx
+++ b/board_fx.sx
@@ -48,7 +48,7 @@ FX_COMBO_LABEL_GAP   :f32: 0.12; // gap (cell units) between the label and +poin
 // order (red, orange, yellow, green, blue, purple). Saturated a touch past the
 // pastel — the low channel is trimmed while the dominant/mid channel is lifted —
 // so every burst pops as a punchier colour without losing luminance.
-fx_tint :: (i: s64) -> Color {
+fx_tint :: (i: i64) -> Color {
     if i == 0 { return Color.{ r = 255, g = 92,  b = 62,  a = 255 }; }
     if i == 1 { return Color.{ r = 255, g = 164, b = 44,  a = 255 }; }
     if i == 2 { return Color.{ r = 255, g = 240, b = 72,  a = 255 }; }
@@ -67,7 +67,7 @@ FX_POPUP_COMBO_HOT   :: Color.{ r = 255, g = 248, b = 214, a = 255 };   // hot n
 // lockstep with the cascade SFX cue. Pure arithmetic, OS-agnostic, and the
 // equivalence to `cascade_cue_index` is locked headlessly (tests/fx_combo.sx).
 FX_COMBO_MAX_LEVEL :: 4;   // == audio.sx COMBO_CLIPS - 1
-fx_combo_level :: (depth: s64) -> s64 {
+fx_combo_level :: (depth: i64) -> i64 {
     if depth <= 1 { return 0; }
     if depth >= FX_COMBO_MAX_LEVEL + 1 { return FX_COMBO_MAX_LEVEL; }
     depth - 1
@@ -76,14 +76,14 @@ fx_combo_level :: (depth: s64) -> s64 {
 // Popup font size for a cascade `depth` rounds deep: a single clear (depth <= 1)
 // uses the plain size; a combo starts at the base combo size and grows one step
 // per combo level past the first, clamped at the deepest level.
-fx_popup_font :: (depth: s64) -> f32 {
+fx_popup_font :: (depth: i64) -> f32 {
     if depth <= 1 { return FX_POPUP_FONT; }
     FX_POPUP_COMBO_FONT + FX_POPUP_COMBO_STEP * cast(f32) (fx_combo_level(depth) - 1)
 }
 
 // Popup colour for a cascade `depth` rounds deep: white for a single clear, else
 // the gold lerped toward a hot near-white as the cascade deepens.
-fx_popup_color :: (depth: s64) -> Color {
+fx_popup_color :: (depth: i64) -> Color {
     if depth <= 1 { return FX_POPUP_COLOR; }
     t := cast(f32) (fx_combo_level(depth) - 1) / cast(f32) (FX_COMBO_MAX_LEVEL - 1);
     Color.{
@@ -101,7 +101,7 @@ fx_lerp_u8 :: (lo: u8, hi: u8, t: f32) -> u8 {
 // Upload an RGBA buffer as a texture, returning its handle. Mirrors
 // board_view.load_texture's upload half but takes an in-memory buffer (the
 // per-colour tinted particle) instead of a file path.
-upload_rgba :: (pixels: [*]u8, w: s32, h: s32, gpu: ?GPU) -> u32 {
+upload_rgba :: (pixels: [*]u8, w: i32, h: i32, gpu: ?GPU) -> u32 {
     if gpu != null {
         return xx gpu.create_texture(w, h, .rgba8, xx pixels);
     }
@@ -128,22 +128,22 @@ BoardFxAssets :: struct {
     }
 
     load :: (self: *BoardFxAssets, gpu: ?GPU) {
-        w : s32 = 0;
-        h : s32 = 0;
-        ch : s32 = 0;
+        w : i32 = 0;
+        h : i32 = 0;
+        ch : i32 = 0;
         src : [*]u8 = xx stbi_load("assets/fx/particle.png", @w, @h, @ch, 4);
         if xx src == 0 {
             out("WARNING: could not load assets/fx/particle.png\n");
             self.loaded = false;
             return;
         }
-        n := cast(s64) w * cast(s64) h;
+        n := cast(i64) w * cast(i64) h;
         buf : [*]u8 = xx context.allocator.alloc_bytes(n * 4);
         // Loop locals are hoisted: a block-scoped local declared inside a body
         // that runs hundreds of thousands of times grows the stack per iteration
         // (sx codegen), so the per-pixel tint loop only ASSIGNS pre-declared vars.
-        i : s64 = 0;
-        o : s64 = 0;
+        i : i64 = 0;
+        o : i64 = 0;
         for 0..GEM_COUNT (t) {
             col := fx_tint(t);
             i = 0;
@@ -168,7 +168,7 @@ BoardFxAssets :: struct {
 FxParticle :: struct {
     col: f32;
     row: f32;
-    tint: s64;
+    tint: i64;
     delay: f32;
     age: f32;
     life: f32;
@@ -184,8 +184,8 @@ FxParticle :: struct {
 FxPopup :: struct {
     col: f32;
     row: f32;
-    points: s64;
-    depth: s64;
+    points: i64;
+    depth: i64;
     delay: f32;
     age: f32;
     life: f32;
@@ -237,7 +237,7 @@ BoardFx :: struct {
                         self.particles.append(FxParticle.{
                             col = cast(f32) col + 0.5,
                             row = cast(f32) row + 0.5,
-                            tint = cast(s64) g,
+                            tint = cast(i64) g,
                             delay = t0 + rdelay,
                             age = 0.0,
                             life = FX_BURST_LIFE,
@@ -250,9 +250,9 @@ BoardFx :: struct {
 
         // One popup for the whole move at the first clear's centroid.
         rd0 := @mv.rounds.items[0];
-        sc : s64 = 0;
-        sr : s64 = 0;
-        cnt : s64 = 0;
+        sc : i64 = 0;
+        sr : i64 = 0;
+        cnt : i64 = 0;
         for 0..BOARD_CELLS (idx) {
             if rd0.matched.cells[idx] {
                 sc += idx % BOARD_COLS;
@@ -275,8 +275,8 @@ BoardFx :: struct {
     // Advance every live FX by `dt` and drop those past their lifetime. Kept
     // simple: compact each list in place by overwriting dead entries.
     tick :: (self: *BoardFx, dt: f32) {
-        w : s64 = 0;
-        i : s64 = 0;
+        w : i64 = 0;
+        i : i64 = 0;
         while i < self.particles.len {
             p := self.particles.items[i];
             p.age += dt;
diff --git a/board_layout.sx b/board_layout.sx
index c250856..0b8672a 100644
--- a/board_layout.sx
+++ b/board_layout.sx
@@ -25,7 +25,7 @@ BoardLayout :: struct {
         };
     }
 
-    cell_frame :: (self: *BoardLayout, col: s64, row: s64) -> Frame {
+    cell_frame :: (self: *BoardLayout, col: i64, row: i64) -> Frame {
         Frame.make(
             self.origin.x + xx col * self.cell_size,
             self.origin.y + xx row * self.cell_size,
@@ -44,8 +44,8 @@ BoardLayout :: struct {
         fx := (p.x - self.origin.x) / self.cell_size;
         fy := (p.y - self.origin.y) / self.cell_size;
         if fx < 0.0 or fy < 0.0 { return null; }
-        col : s64 = xx fx;
-        row : s64 = xx fy;
+        col : i64 = xx fx;
+        row : i64 = xx fy;
         if col >= BOARD_COLS or row >= BOARD_ROWS { return null; }
         Cell.{ col = col, row = row }
     }
diff --git a/board_view.sx b/board_view.sx
index a182fe9..f3aaa62 100644
--- a/board_view.sx
+++ b/board_view.sx
@@ -126,7 +126,7 @@ BoardAssets :: struct {
         self.loaded = self.bg_tex != 0 and self.cell_tex != 0 and self.gems_tex != 0;
     }
 
-    gem_uv :: (self: *BoardAssets, index: s64) -> GemUV {
+    gem_uv :: (self: *BoardAssets, index: i64) -> GemUV {
         u0 : f32 = xx index * self.cell_u;
         GemUV.{
             uv_min = Point.{ x = u0, y = 0.0 },
@@ -139,9 +139,9 @@ BoardAssets :: struct {
 // failure). When a GPU backend is bound (iOS Metal) it owns the upload; the
 // desktop GL path falls back to a plain GL_TEXTURE_2D.
 load_texture :: (path: [:0]u8, gpu: ?GPU) -> u32 {
-    w : s32 = 0;
-    h : s32 = 0;
-    ch : s32 = 0;
+    w : i32 = 0;
+    h : i32 = 0;
+    ch : i32 = 0;
     pixels := stbi_load(path, @w, @h, @ch, 4);
     if pixels == null {
         out("WARNING: could not load texture: ");
@@ -237,7 +237,7 @@ BoardView :: struct {
     safe: EdgeInsets;
     // Seed for `restart`: the same fixed seed main seeded the board with, so the
     // restart button reproduces the identical starting level.
-    seed: s64;
+    seed: i64;
     // FPS dev overlay (P20.1). `fps_on` gates the corner readout (off by default,
     // set only by the M3TE_FPS env pin); `fps` is the smoothed reciprocal frame
     // rate computed in the frame loop. Purely a render overlay.
@@ -266,7 +266,7 @@ BoardView :: struct {
     }
 
     // Draw gem `gem_index`'s sprite-sheet column into `gf`.
-    draw_gem :: (self: *BoardView, ctx: *RenderContext, gf: Frame, gem_index: s64) {
+    draw_gem :: (self: *BoardView, ctx: *RenderContext, gf: Frame, gem_index: i64) {
         uv := self.assets.gem_uv(gem_index);
         ctx.add_image_uv(gf, self.assets.gems_tex, uv.uv_min, uv.uv_max);
     }
@@ -285,7 +285,7 @@ BoardView :: struct {
 
     // Frame for a gem shrunk by `scale` about its cell centre — the clear
     // scale-out. At scale 0 the gem is a zero-size frame (gone).
-    gem_frame_scaled :: (self: *BoardView, col: s64, row: s64, dim: f32, scale: f32) -> Frame {
+    gem_frame_scaled :: (self: *BoardView, col: i64, row: i64, dim: f32, scale: f32) -> Frame {
         cs := self.layout.cell_size;
         cx := self.layout.origin.x + cast(f32) col * cs + cs * 0.5;
         cy := self.layout.origin.y + cast(f32) row * cs + cs * 0.5;
@@ -297,7 +297,7 @@ BoardView :: struct {
     // sprite is scaled about its cell centre and nudged by the pose offset (both
     // in cell units). A resting pose reproduces gem_frame exactly, so the t==0
     // idle pose draws identically to the static sprite.
-    gem_pose_frame :: (self: *BoardView, col: s64, row: s64, dim: f32, pose: GemPose) -> Frame {
+    gem_pose_frame :: (self: *BoardView, col: i64, row: i64, dim: f32, pose: GemPose) -> Frame {
         cs := self.layout.cell_size;
         cx := self.layout.origin.x + (cast(f32) col + 0.5) * cs + pose.dx * cs;
         cy := self.layout.origin.y + (cast(f32) row + 0.5) * cs + pose.dy * cs;
@@ -311,7 +311,7 @@ BoardView :: struct {
     // — the wide-and-short landing impact. sq==0 reproduces gem_frame's centred
     // placement EXACTLY, so a gem still mid-fall (or one that never moved) draws
     // byte-identically to the plain fall; only a landed gem flattens.
-    gem_squash_frame :: (self: *BoardView, col: s64, frow: f32, dim: f32, sq: f32) -> Frame {
+    gem_squash_frame :: (self: *BoardView, col: i64, frow: f32, dim: f32, sq: f32) -> Frame {
         cs := self.layout.cell_size;
         cx := self.layout.origin.x + (cast(f32) col + 0.5) * cs;
         cy := self.layout.origin.y + (frow + 0.5) * cs;
@@ -323,7 +323,7 @@ BoardView :: struct {
     // The per-gem animation pose for a settled cell: the always-on idle breath,
     // plus a squash-bounce if the cell landed recently, plus a pop if it is the
     // selected cell. Purely visual — composed from gem_anim's pure functions.
-    gem_pose_at :: (self: *BoardView, col: s64, row: s64) -> GemPose {
+    gem_pose_at :: (self: *BoardView, col: i64, row: i64) -> GemPose {
         pose := idle_pose(self.motion.clock, col, row);
 
         sq := land_squash(self.motion.land_local(Board.idx(col, row)));
@@ -347,7 +347,7 @@ BoardView :: struct {
     // (land_squash → 0, so it draws unsquashed) and one that never moved reads 0.
     // render_fall passes the current round; render_clear the previous (its board is
     // that round's `after`), so the one bounce plays on across the fall→clear seam.
-    rest_squash :: (self: *BoardView, i: s64, kmax: s64, elapsed: f32) -> f32 {
+    rest_squash :: (self: *BoardView, i: i64, kmax: i64, elapsed: f32) -> f32 {
         m := delivering_round(@self.anim.move, i, kmax);
         if m < 0 { return 0.0; }
         col := i % BOARD_COLS;
@@ -363,7 +363,7 @@ BoardView :: struct {
                 if g != .empty {
                     pose := self.gem_pose_at(col, row);
                     gf := self.gem_pose_frame(col, row, dim, pose);
-                    self.draw_gem(ctx, gf, cast(s64) g);
+                    self.draw_gem(ctx, gf, cast(i64) g);
                 }
             }
         }
@@ -436,7 +436,7 @@ BoardView :: struct {
                 if g != .empty {
                     sq := self.rest_squash(i, last, e);
                     gf := self.gem_squash_frame(i % BOARD_COLS, cast(f32) (i / BOARD_COLS), dim, sq);
-                    self.draw_gem(ctx, gf, cast(s64) g);
+                    self.draw_gem(ctx, gf, cast(i64) g);
                 }
             }
         }
@@ -457,7 +457,7 @@ BoardView :: struct {
             g := mv.pre[i];
             if g != .empty {
                 gf := self.gem_frame(cast(f32) (i % BOARD_COLS), cast(f32) (i / BOARD_COLS), inset, dim);
-                self.draw_gem(ctx, gf, cast(s64) g);
+                self.draw_gem(ctx, gf, cast(i64) g);
             }
         }
 
@@ -482,18 +482,18 @@ BoardView :: struct {
         ga := mv.pre[ai];
         if ga != .empty {
             gf := self.gem_frame(afc + (bfc - afc) * p, afr + (bfr - afr) * p, inset, dim);
-            self.draw_gem(ctx, gf, cast(s64) ga);
+            self.draw_gem(ctx, gf, cast(i64) ga);
         }
         gb := mv.pre[bi];
         if gb != .empty {
             gf := self.gem_frame(bfc + (afc - bfc) * p, bfr + (afr - bfr) * p, inset, dim);
-            self.draw_gem(ctx, gf, cast(s64) gb);
+            self.draw_gem(ctx, gf, cast(i64) gb);
         }
     }
 
     // Clear segment: matched gems pop outward then collapse to nothing (a
     // satisfying pop, composing with the particle burst); the rest hold position.
-    render_clear :: (self: *BoardView, ctx: *RenderContext, rd: *AnimRound, k: s64, e: f32, dim: f32, t: f32) {
+    render_clear :: (self: *BoardView, ctx: *RenderContext, rd: *AnimRound, k: i64, e: f32, dim: f32, t: f32) {
         span := clear_diag_span(@rd.matched);
         for 0..BOARD_CELLS (i) {
             g := rd.before[i];
@@ -507,7 +507,7 @@ BoardView :: struct {
                 // reaches scale 0 by t==1, keeping the seam to the fall clean.
                 pop := clear_pop_scale(clear_ripple_t(t, clear_rank(span, col, row)));
                 gf := self.gem_frame_scaled(col, row, dim, pop);
-                self.draw_gem(ctx, gf, cast(s64) g);
+                self.draw_gem(ctx, gf, cast(i64) g);
             } else {
                 // before[k] is round k-1's settled board, so a survivor here still
                 // carries the bounce from the round that dropped it in — continue it
@@ -515,7 +515,7 @@ BoardView :: struct {
                 // (nothing has fallen yet), keeping that frame byte-identical.
                 sq := self.rest_squash(i, k - 1, e);
                 gf := self.gem_squash_frame(col, cast(f32) row, dim, sq);
-                self.draw_gem(ctx, gf, cast(s64) g);
+                self.draw_gem(ctx, gf, cast(i64) g);
             }
         }
     }
@@ -593,7 +593,7 @@ BoardView :: struct {
     // lockstep row; ease_in_cubic pins each column's f(1)=1, and fall_stagger_t
     // guarantees every column reaches 1 by t==1, so each gem lands exactly on its
     // cell and the seam to the next round / settled board stays invisible.
-    render_fall :: (self: *BoardView, ctx: *RenderContext, rd: *AnimRound, k: s64, e: f32, dim: f32, t: f32) {
+    render_fall :: (self: *BoardView, ctx: *RenderContext, rd: *AnimRound, k: i64, e: f32, dim: f32, t: f32) {
         for 0..BOARD_CELLS (i) {
             g := rd.after[i];
             if g == .empty { continue; }
@@ -608,7 +608,7 @@ BoardView :: struct {
             // has reached its cell flattens wide-and-short, then wobbles out.
             sq := self.rest_squash(i, k, e);
             gf := self.gem_squash_frame(col, cur_row, dim, sq);
-            self.draw_gem(ctx, gf, cast(s64) g);
+            self.draw_gem(ctx, gf, cast(i64) g);
         }
     }
 
@@ -668,7 +668,7 @@ BoardView :: struct {
     // pin) is set, so the unset render path is byte-identical. A bright halo under
     // the dark text keeps the digits legible over the light background art.
     render_fps_overlay :: (self: *BoardView, ctx: *RenderContext, frame: Frame) {
-        n := cast(s64) (self.fps + 0.5);
+        n := cast(i64) (self.fps + 0.5);
         txt := format("FPS {}", n);
         sz := measure_text(txt, FPS_FONT);
         x := frame.origin.x + self.safe.left + FPS_PAD;
diff --git a/docs/std-gaps.md b/docs/std-gaps.md
index 271858e..8f8e9e1 100644
--- a/docs/std-gaps.md
+++ b/docs/std-gaps.md
@@ -25,9 +25,9 @@ the step asks for an honest accounting.
 
 ## Category: Numerics / parsing
 
-### 1. String → number parsing (`parse_s64`, `parse_f32`)
-- **m3te location:** `main.sx:156` (`parse_s64`), `main.sx:122` (`parse_f32`).
-- **What it does:** decimal ASCII `string` → `s64` / `f32` (sign + integer +
+### 1. String → number parsing (`parse_i64`, `parse_f32`)
+- **m3te location:** `main.sx:156` (`parse_i64`), `main.sx:122` (`parse_f32`).
+- **What it does:** decimal ASCII `string` → `i64` / `f32` (sign + integer +
   optional fractional part).
 - **Why general-purpose:** the exact inverse of the formatters everyone already
   uses; needed by any program that reads numbers from argv, env, config, or a
@@ -46,7 +46,7 @@ the step asks for an honest accounting.
 - **m3te location:** `board.sx:55` (`Rng` struct: `next_u32` `board.sx:59`,
   `next_range` `board.sx:66`), `board.sx:71` (`rng_seeded`), constants
   `board.sx:51-53`.
-- **What it does:** a 32-bit linear-congruential generator carried in `s64`
+- **What it does:** a 32-bit linear-congruential generator carried in `i64`
   and masked to 32 bits — `next_u32()`, `next_range(n)` (uniform-ish `[0,n)`),
   `rng_seeded(seed)`.
 - **Why general-purpose:** a seedable, reproducible RNG is a textbook stdlib
@@ -172,7 +172,7 @@ them, so they are explicitly **not** counted above:
 
 ## Summary (top gaps, ranked)
 
-1. **String → number parsing** (`parse_s64` / `parse_f32`) — clean, universally
+1. **String → number parsing** (`parse_i64` / `parse_f32`) — clean, universally
    needed, the missing inverse of the existing formatters.
 2. **Seedable PRNG** (`Rng` LCG) — textbook stdlib primitive, entirely absent.
 3. **`from_cstr` C-string bridge** (+ public `strlen`) — the most-repeated FFI
diff --git a/gem_anim.sx b/gem_anim.sx
index 5c22774..078e416 100644
--- a/gem_anim.sx
+++ b/gem_anim.sx
@@ -38,11 +38,11 @@ IDLE_BOB_A   :f32: 0.024;  // vertical bob amplitude (cell units)
 IDLE_RAMP    :f32: 0.45;   // seconds to ease the idle up from full rest
 
 // Smooth per-cell phase: a diagonal gradient wrapped into one breath period.
-gem_idle_phase :: (col: s64, row: s64) -> f32 {
+gem_idle_phase :: (col: i64, row: i64) -> f32 {
     cast(f32) ((col * 2 + row * 3) % 8) / 8.0 * TAU
 }
 
-idle_pose :: (t: f32, col: s64, row: s64) -> GemPose {
+idle_pose :: (t: f32, col: i64, row: i64) -> GemPose {
     ramp := clamp(t / IDLE_RAMP, 0.0, 1.0);
     w := t / IDLE_PERIOD * TAU + gem_idle_phase(col, row);
     s := IDLE_SCALE_A * sin(w) * ramp;
@@ -135,7 +135,7 @@ GemMotion :: struct {
         for 0..BOARD_CELLS (i) { self.land_at[i] = -1000.0; }
     }
 
-    stamp_land :: (self: *GemMotion, i: s64) {
+    stamp_land :: (self: *GemMotion, i: i64) {
         self.stamp_land_at(i, self.clock);
     }
 
@@ -143,11 +143,11 @@ GemMotion :: struct {
     // can BACK-DATE the stamp to when the gem actually touched down mid-fall (each
     // column lands at a staggered instant): land_squash then resumes the per-round
     // bounce exactly where render_fall left it, with no double-pop at the seam.
-    stamp_land_at :: (self: *GemMotion, i: s64, at: f32) {
+    stamp_land_at :: (self: *GemMotion, i: i64, at: f32) {
         self.land_at[i] = at;
     }
 
-    land_local :: (self: *GemMotion, i: s64) -> f32 {
+    land_local :: (self: *GemMotion, i: i64) -> f32 {
         self.clock - self.land_at[i]
     }
 }
diff --git a/main.sx b/main.sx
index dda3efe..520b61b 100644
--- a/main.sx
+++ b/main.sx
@@ -117,40 +117,40 @@ build_ui :: () -> View {
 // be captured without injecting a tap. Absent → normal live behaviour.
 read_env :: (name: [:0]u8) -> ?string {
     p := getenv(name);
-    addr : s64 = xx p;
+    addr : i64 = xx p;
     if addr == 0 { return null; }
-    n := cast(s64) strlen(p);
+    n := cast(i64) strlen(p);
     if n == 0 { return ""; }
     buf := cstring(n);
     memcpy(buf.ptr, xx p, n);
     buf
 }
 
-// Digit arithmetic runs entirely in s64; the result converts to f32 only once at
+// Digit arithmetic runs entirely in i64; the result converts to f32 only once at
 // the end. Doing the digit math in f32 would unify the ASCII literals (45/46/48/
 // 57) to f32 across the comparisons, which mis-types the byte compares.
 parse_f32 :: (s: string) -> f32 {
-    i : s64 = 0;
+    i : i64 = 0;
     neg : bool = false;
     if s.len > 0 {
-        c0 : s64 = xx s[0];
+        c0 : i64 = xx s[0];
         if c0 == 45 { neg = true; i = 1; }     // '-'
     }
-    intval : s64 = 0;
+    intval : i64 = 0;
     while i < s.len {
-        c : s64 = xx s[i];
+        c : i64 = xx s[i];
         if c < 48 or c > 57 { break; }
         intval = intval * 10 + (c - 48);
         i += 1;
     }
-    fracval : s64 = 0;
-    fracdiv : s64 = 1;
+    fracval : i64 = 0;
+    fracdiv : i64 = 1;
     if i < s.len {
-        d : s64 = xx s[i];
+        d : i64 = xx s[i];
         if d == 46 {                           // '.'
             i += 1;
             while i < s.len {
-                c : s64 = xx s[i];
+                c : i64 = xx s[i];
                 if c < 48 or c > 57 { break; }
                 fracval = fracval * 10 + (c - 48);
                 fracdiv = fracdiv * 10;
@@ -163,11 +163,11 @@ parse_f32 :: (s: string) -> f32 {
     v
 }
 
-parse_s64 :: (s: string) -> s64 {
-    i : s64 = 0;
-    v : s64 = 0;
+parse_i64 :: (s: string) -> i64 {
+    i : i64 = 0;
+    v : i64 = 0;
     while i < s.len {
-        c : s64 = xx s[i];
+        c : i64 = xx s[i];
         if c < 48 or c > 57 { break; }
         v = v * 10 + (c - 48);
         i += 1;
@@ -405,7 +405,7 @@ main :: () -> void {
         g_motion.clock = parse_f32(t);
     }
     if sc := read_env("M3TE_SELECT") {
-        idx := parse_s64(sc);
+        idx := parse_i64(sc);
         if idx >= 0 and idx < BOARD_CELLS {
             g_sel.active = true;
             g_sel.cell = Cell.{ col = idx % BOARD_COLS, row = idx / BOARD_COLS };
@@ -418,7 +418,7 @@ main :: () -> void {
     // committed golden stay byte-identical. Purely a render overlay — no board /
     // score / move / animation state changes and it never gates input.
     if fp := read_env("M3TE_FPS") {
-        if parse_s64(fp) != 0 { g_fps_on = true; }
+        if parse_i64(fp) != 0 { g_fps_on = true; }
     }
 
     // Match-FX capture hook (P11.1). The bursts/popups spawn off a committed move,
@@ -433,7 +433,7 @@ main :: () -> void {
     if fx := read_env("M3TE_FX") {
         swaps := legal_swaps(g_board);
         if swaps.len > 0 {
-            n := parse_s64(fx);
+            n := parse_i64(fx);
             if n < 1 { n = 1; }
             if n > swaps.len { n = swaps.len; }
             sw := swaps.items[n - 1];
@@ -457,7 +457,7 @@ main :: () -> void {
     if bs := read_env("M3TE_BADSWAP") {
         bad := illegal_swaps(g_board);
         if bad.len > 0 {
-            n := parse_s64(bs);
+            n := parse_i64(bs);
             if n < 1 { n = 1; }
             if n > bad.len { n = bad.len; }
             sw := bad.items[n - 1];
@@ -473,10 +473,10 @@ main :: () -> void {
     // M3TE_MOVE_LIMIT=0 makes it read LOST (budget spent below the goal). With
     // M3TE_RESTART set non-zero the board is then restart()-ed, capturing the
     // fresh in_progress board the restart button produces.
-    if tg := read_env("M3TE_TARGET") { g_board.target_score = parse_s64(tg); }
-    if ml := read_env("M3TE_MOVE_LIMIT") { g_board.move_limit = parse_s64(ml); }
+    if tg := read_env("M3TE_TARGET") { g_board.target_score = parse_i64(tg); }
+    if ml := read_env("M3TE_MOVE_LIMIT") { g_board.move_limit = parse_i64(ml); }
     if rs := read_env("M3TE_RESTART") {
-        if parse_s64(rs) != 0 { g_board.restart(BOARD_SEED); }
+        if parse_i64(rs) != 0 { g_board.restart(BOARD_SEED); }
     }
 
     g_pipeline.set_body(closure(build_ui));
diff --git a/tests/anim_plan.sx b/tests/anim_plan.sx
index 97a2e4a..ebcb84b 100644
--- a/tests/anim_plan.sx
+++ b/tests/anim_plan.sx
@@ -30,8 +30,8 @@ boards_equal :: (x: *Board, y: *Board) -> bool {
     true
 }
 
-main :: () -> s32 {
-    fails : s64 = 0;
+main :: () -> i32 {
+    fails : i64 = 0;
 
     // ── Legal swap: plan == model, timeline ends on the model ───────────────
     // (5,4)->(6,4): brings R into (5,4), completing R,R,R across cols 3-5 of row
diff --git a/tests/arith.sx b/tests/arith.sx
index 1505493..b2f3c70 100644
--- a/tests/arith.sx
+++ b/tests/arith.sx
@@ -4,7 +4,7 @@
 #import "modules/std.sx";
 t :: #import "test.sx";
 
-main :: () -> s32 {
+main :: () -> i32 {
     t.expect(2 + 2 == 4, "two plus two is four");
     t.expect(7 % 3 == 1, "seven mod three is one");
     t.expect(10 - 4 == 6, "ten minus four is six");
diff --git a/tests/banner_layout.sx b/tests/banner_layout.sx
index b568b9a..4fff51a 100644
--- a/tests/banner_layout.sx
+++ b/tests/banner_layout.sx
@@ -19,11 +19,11 @@
 
 irect :: (f: Frame) -> string {
     format("({},{},{},{})",
-        cast(s64) f.origin.x, cast(s64) f.origin.y,
-        cast(s64) f.size.width, cast(s64) f.size.height)
+        cast(i64) f.origin.x, cast(i64) f.origin.y,
+        cast(i64) f.size.width, cast(i64) f.size.height)
 }
 
-main :: () -> s32 {
+main :: () -> i32 {
     // 800×600, no safe inset → 600px square grid, cell 75, origin (100,0): the
     // same layout tests/hit_test.sx pins, so the numbers are checkable by hand.
     lay : BoardLayout = ---;
@@ -36,18 +36,18 @@ main :: () -> s32 {
     print("title {}\n", irect(bl.title));
     print("button {}\n", irect(bl.button));
 
-    fails : s64 = 0;
+    fails : i64 = 0;
 
     // The button is horizontally centered on the grid (centred banner).
     bcx := bl.button.mid_x();
-    if cast(s64) bcx != cast(s64) grid.mid_x() { fails += 1; }
-    print("button mid_x {} grid mid_x {}\n", cast(s64) bcx, cast(s64) grid.mid_x());
+    if cast(i64) bcx != cast(i64) grid.mid_x() { fails += 1; }
+    print("button mid_x {} grid mid_x {}\n", cast(i64) bcx, cast(i64) grid.mid_x());
 
     // The whole button sits inside the panel — its four corners are contained,
     // so it can never spill outside the drawn card.
     bx0 := bl.button.origin.x;  by0 := bl.button.origin.y;
     bx1 := bl.button.max_x();    by1 := bl.button.max_y();
-    corners_in : s64 = 0;
+    corners_in : i64 = 0;
     if bl.panel.contains(Point.{ x = bx0, y = by0 }) { corners_in += 1; }
     if bl.panel.contains(Point.{ x = bx1, y = by0 }) { corners_in += 1; }
     if bl.panel.contains(Point.{ x = bx0, y = by1 }) { corners_in += 1; }
@@ -67,7 +67,7 @@ main :: () -> s32 {
     // in the button, so each leaves the level frozen.
     corner_cell := Point.{ x = grid.origin.x + lay.cell_size * 0.5, y = grid.origin.y + lay.cell_size * 0.5 };
     outside := Point.{ x = bl.panel.origin.x - 5.0, y = bl.panel.mid_y() };
-    off_hits : s64 = 0;
+    off_hits : i64 = 0;
     if bl.button.contains(corner_cell) { off_hits += 1; }
     if bl.button.contains(outside)     { off_hits += 1; }
     if off_hits != 0 { fails += 1; }
diff --git a/tests/board_init.sx b/tests/board_init.sx
index 9b4b829..9ad26ad 100644
--- a/tests/board_init.sx
+++ b/tests/board_init.sx
@@ -10,8 +10,8 @@ SEED :: 1337;
 // Count every horizontal or vertical window of three consecutive same-type
 // gems. A correctly initialized board has zero. This walks the finished board
 // independently of the placement logic, so it's a real check, not a tautology.
-count_three_runs :: (b: *Board) -> s32 {
-    runs : s32 = 0;
+count_three_runs :: (b: *Board) -> i32 {
+    runs : i32 = 0;
     for 0..BOARD_ROWS (row) {
         for 0..(BOARD_COLS - 2) (col) {
             g := b.at(col, row);
@@ -27,7 +27,7 @@ count_three_runs :: (b: *Board) -> s32 {
     runs
 }
 
-main :: () -> s32 {
+main :: () -> i32 {
     board : Board = ---;
     board.init(SEED);
 
diff --git a/tests/cascade.sx b/tests/cascade.sx
index 6177758..3fa9b60 100644
--- a/tests/cascade.sx
+++ b/tests/cascade.sx
@@ -84,7 +84,7 @@ checker_board :: () -> Board {
     b
 }
 
-main :: () -> s32 {
+main :: () -> i32 {
     print("== cascade (resolution loop) ==\n");
 
     // Drive the loop one round at a time so each post-round board is visible in
@@ -94,7 +94,7 @@ main :: () -> s32 {
     out(board_dump(@b));
 
     depth := 0;
-    counts := List(s64).{};
+    counts := List(i64).{};
     while true {
         n := resolve_step(@b);
         if n == 0 { break; }
diff --git a/tests/cascade_cue.sx b/tests/cascade_cue.sx
index 853e179..46e63de 100644
--- a/tests/cascade_cue.sx
+++ b/tests/cascade_cue.sx
@@ -8,13 +8,13 @@
 #import "modules/std.sx";
 #import "audio.sx";
 
-main :: () -> s32 {
+main :: () -> i32 {
     print("== cascade cue selection (depth -> combo cue) ==\n");
 
     // Walk a representative depth range (0..9) so both clamps and the monotonic
     // middle are visible: depths 0,1 pin to the first cue; depths >= 5 pin to
     // the last; 2,3,4 step up one cue at a time.
-    prev : s64 = -1;
+    prev : i64 = -1;
     for 0..10 (depth) {
         idx := cascade_cue_index(depth);
         print("depth {} -> idx {} ({})\n", depth, idx, cascade_cue_name(idx));
diff --git a/tests/cascade_rounds.sx b/tests/cascade_rounds.sx
index decf440..182ff86 100644
--- a/tests/cascade_rounds.sx
+++ b/tests/cascade_rounds.sx
@@ -13,7 +13,7 @@
 #import "board_anim.sx";
 #import "audio.sx";
 
-main :: () -> s32 {
+main :: () -> i32 {
     print("== per-round cascade cue timing ==\n");
 
     // `cascade_rounds_started` = how many cascade rounds have BEGUN clearing by
@@ -21,7 +21,7 @@ main :: () -> s32 {
     // Round k (0-based) starts clearing at 0.16 + k*0.36; sampled safely INSIDE
     // each round window so the integer step is unambiguous. Locked for 5 rounds.
     print("-- started-count across a 5-round chain --\n");
-    rounds : s64 = 5;
+    rounds : i64 = 5;
     print("e=0.00 -> {}\n", cascade_rounds_started(0.00, rounds));
     print("e=0.10 -> {}\n", cascade_rounds_started(0.10, rounds));
     print("e=0.20 -> {}\n", cascade_rounds_started(0.20, rounds));
@@ -37,7 +37,7 @@ main :: () -> s32 {
     // ascending. This IS the loop main's frame loop runs; the emitted run is the
     // locked acceptance ordering.
     print("-- ascending per-round run --\n");
-    fired : s64 = 0;
+    fired : i64 = 0;
     elapsed : f32 = 0.0;
     while fired < rounds {
         started := cascade_rounds_started(elapsed, rounds);
diff --git a/tests/clear.sx b/tests/clear.sx
index b229035..fb7d9ac 100644
--- a/tests/clear.sx
+++ b/tests/clear.sx
@@ -38,7 +38,7 @@ load_board :: (rows: []string) -> Board {
 // Detect→clear one scene, snapshot before/after, and assert the three clear
 // invariants against the matched-cell set: every flagged cell is now a hole,
 // every unflagged cell is unchanged, and the returned count is exact.
-scene :: (name: string, rows: []string, want_cleared: s64) {
+scene :: (name: string, rows: []string, want_cleared: i64) {
     b := load_board(rows);
     orig := load_board(rows);          // pristine copy for the unchanged check
 
@@ -65,7 +65,7 @@ scene :: (name: string, rows: []string, want_cleared: s64) {
     t.expect(cleared == want_cleared, concat(name, ": cleared count exact"));
 }
 
-main :: () -> s32 {
+main :: () -> i32 {
     print("== clear (detect -> clear) ==\n");
 
     // Single horizontal 3-run (row 3, cols 2-4) → three holes there only.
diff --git a/tests/collapse.sx b/tests/collapse.sx
index 934d7e1..ebd1f61 100644
--- a/tests/collapse.sx
+++ b/tests/collapse.sx
@@ -79,7 +79,7 @@ scene :: (name: string, rows: []string, want_moved: bool) {
     t.expect(moved == want_moved, concat(name, ": moved flag exact"));
 }
 
-main :: () -> s32 {
+main :: () -> i32 {
     print("== collapse (gravity) ==\n");
 
     // Eight independent columns, one case each (top-to-bottom):
diff --git a/tests/combo.sx b/tests/combo.sx
index f902dcc..da3341e 100644
--- a/tests/combo.sx
+++ b/tests/combo.sx
@@ -31,7 +31,7 @@ char_to_gem :: (c: u8) -> Gem {
 
 // Load an 8x8 board from `rows` (top row first, each exactly BOARD_COLS chars),
 // seeded RNG, running score zeroed so `board.score` ends equal to the payout.
-load_board :: (rows: []string, seed: s64) -> Board {
+load_board :: (rows: []string, seed: i64) -> Board {
     b : Board = ---;
     for 0..BOARD_ROWS (row) {
         line := rows[row];
@@ -51,14 +51,14 @@ load_board :: (rows: []string, seed: s64) -> Board {
 // identical board awards `want_mult` into `Board.score` and reports it as
 // `Cascade.awarded` at the same depth. A depth-1 settle must equal the flat sum
 // (no bonus); a deeper chain must strictly exceed it.
-scene :: (name: string, rows: []string, seed: s64, want_flat: s64, want_mult: s64) {
+scene :: (name: string, rows: []string, seed: i64, want_flat: i64, want_mult: i64) {
     print("== {} ==\n", name);
     b := load_board(rows, seed);
     out(board_dump(@b));
 
-    flat : s64 = 0;
-    mult : s64 = 0;
-    depth : s64 = 0;
+    flat : i64 = 0;
+    mult : i64 = 0;
+    depth : i64 = 0;
     while true {
         base := score_round(@b);
         n := resolve_step(@b);
@@ -90,7 +90,7 @@ scene :: (name: string, rows: []string, seed: s64, want_flat: s64, want_mult: s6
     t.expect(b2.score == want_mult, concat(name, ": resolve accumulates into board.score"));
 }
 
-main :: () -> s32 {
+main :: () -> i32 {
     print("== combo (cascade multiplier) ==\n");
 
     // Single-round clear (seed 0): one RRR clears and the refill makes no new
diff --git a/tests/easing.sx b/tests/easing.sx
index 3289556..31b1749 100644
--- a/tests/easing.sx
+++ b/tests/easing.sx
@@ -19,8 +19,8 @@
 fabs :: (x: f32) -> f32 { if x < 0.0 then 0.0 - x else x }
 approx :: (a: f32, b: f32) -> bool { fabs(a - b) < 0.0001 }
 
-main :: () -> s32 {
-    fails : s64 = 0;
+main :: () -> i32 {
+    fails : i64 = 0;
 
     // 1. Endpoints are locked: every curve starts/ends exactly on its rest value
     //    (the in/out curves at 1, the spring at 1, the squash envelope at 0).
diff --git a/tests/fx_combo.sx b/tests/fx_combo.sx
index 7ec64df..f9b8f63 100644
--- a/tests/fx_combo.sx
+++ b/tests/fx_combo.sx
@@ -13,14 +13,14 @@
 #import "modules/std.sx";
 #import "board_fx.sx";
 
-main :: () -> s32 {
+main :: () -> i32 {
     print("== combo emphasis selection (depth -> fx level / popup font) ==\n");
 
     // The cascade-cue index per depth 0..9, copied from cascade_cue.stdout. The
     // FX level must equal this entry for entry — the audio/visual lockstep.
-    expect_level : [10]s64 = .{ 0, 0, 1, 2, 3, 4, 4, 4, 4, 4 };
+    expect_level : [10]i64 = .{ 0, 0, 1, 2, 3, 4, 4, 4, 4, 4 };
 
-    prev : s64 = -1;
+    prev : i64 = -1;
     for 0..10 (depth) {
         lvl := fx_combo_level(depth);
         font := fx_popup_font(depth);
diff --git a/tests/gem_pose.sx b/tests/gem_pose.sx
index 70db336..b019043 100644
--- a/tests/gem_pose.sx
+++ b/tests/gem_pose.sx
@@ -18,8 +18,8 @@
 fabs :: (x: f32) -> f32 { if x < 0.0 then 0.0 - x else x }
 approx :: (a: f32, b: f32) -> bool { fabs(a - b) < 0.0001 }
 
-main :: () -> s32 {
-    fails : s64 = 0;
+main :: () -> i32 {
+    fails : i64 = 0;
 
     // 1. t==0 idle pose is EXACTLY rest for every cell (the determinism invariant).
     print("== idle t=0 is rest for all cells ==\n");
diff --git a/tests/hit_test.sx b/tests/hit_test.sx
index b2887df..327b0ef 100644
--- a/tests/hit_test.sx
+++ b/tests/hit_test.sx
@@ -14,19 +14,19 @@
 #import "board.sx";
 #import "board_layout.sx";
 
-main :: () -> s32 {
+main :: () -> i32 {
     // 800×600 with no safe inset → a 600px square grid, cell 75, centered: the
     // grid origin lands at (100, 0). Integer math keeps the dump deterministic.
     lay : BoardLayout = ---;
     lay.compute(Frame.make(0.0, 0.0, 800.0, 600.0), EdgeInsets.zero());
 
     print("grid origin ({},{}) cell {}\n",
-        cast(s64) lay.origin.x, cast(s64) lay.origin.y, cast(s64) lay.cell_size);
+        cast(i64) lay.origin.x, cast(i64) lay.origin.y, cast(i64) lay.cell_size);
 
-    fails : s64 = 0;
+    fails : i64 = 0;
 
     // Every cell center must map back to its own cell.
-    hits : s64 = 0;
+    hits : i64 = 0;
     for 0..BOARD_ROWS (row) {
         for 0..BOARD_COLS (col) {
             cf := lay.cell_frame(col, row);
@@ -42,8 +42,8 @@ main :: () -> s32 {
     // A cell's top-left corner belongs to that cell (the leading edge is
     // inclusive), so corner-of-(3,5) resolves to (3,5).
     corner := Point.{ x = lay.origin.x + 3.0 * lay.cell_size, y = lay.origin.y + 5.0 * lay.cell_size };
-    corner_col : s64 = -1;
-    corner_row : s64 = -1;
+    corner_col : i64 = -1;
+    corner_row : i64 = -1;
     if h := lay.point_to_cell(corner) { corner_col = h.col; corner_row = h.row; }
     if corner_col != 3 or corner_row != 5 { fails += 1; }
     print("corner maps to ({},{})\n", corner_col, corner_row);
@@ -53,7 +53,7 @@ main :: () -> s32 {
     off_left  := Point.{ x = lay.origin.x - 5.0,                       y = lay.origin.y + 10.0 };
     off_above := Point.{ x = lay.origin.x + 10.0,                      y = lay.origin.y - 5.0 };
     off_right := Point.{ x = lay.origin.x + 8.0 * lay.cell_size + 1.0, y = lay.origin.y + 10.0 };
-    on_board : s64 = 0;
+    on_board : i64 = 0;
     if h := lay.point_to_cell(off_left)  { on_board += 1; print("off_left  hit ({},{})\n", h.col, h.row); }
     if h := lay.point_to_cell(off_above) { on_board += 1; print("off_above hit ({},{})\n", h.col, h.row); }
     if h := lay.point_to_cell(off_right) { on_board += 1; print("off_right hit ({},{})\n", h.col, h.row); }
diff --git a/tests/level.sx b/tests/level.sx
index fc1a4aa..a0b3790 100644
--- a/tests/level.sx
+++ b/tests/level.sx
@@ -34,7 +34,7 @@ char_to_gem :: (c: u8) -> Gem {
 // Load an 8x8 board from `rows` (top row first, each exactly BOARD_COLS chars),
 // seeded RNG, running score zeroed, the turn counters reset to a fresh game, and
 // the per-level goal set.
-load_board :: (rows: []string, seed: s64, move_limit: s64, target_score: s64) -> Board {
+load_board :: (rows: []string, seed: i64, move_limit: i64, target_score: i64) -> Board {
     b : Board = ---;
     for 0..BOARD_ROWS (row) {
         line := rows[row];
@@ -55,7 +55,7 @@ boards_equal :: (a: *Board, b: *Board) -> bool {
     true
 }
 
-main :: () -> s32 {
+main :: () -> i32 {
     print("== level (turn / goal state machine) ==\n");
 
     // ── Start: a fresh seeded board reads in_progress with the default goal ──
diff --git a/tests/match_detect.sx b/tests/match_detect.sx
index 573a4d8..bcc888a 100644
--- a/tests/match_detect.sx
+++ b/tests/match_detect.sx
@@ -20,7 +20,7 @@ char_to_gem :: (c: u8) -> Gem {
 // Build a scene: load an 8x8 board from `rows` (top row first, each exactly
 // BOARD_COLS gem characters), detect matches, print board + matched dump, and
 // assert the matched-cell count.
-scene :: (name: string, rows: []string, want_count: s64) {
+scene :: (name: string, rows: []string, want_count: i64) {
     b : Board = ---;
     for 0..BOARD_ROWS (row) {
         line := rows[row];
@@ -38,7 +38,7 @@ scene :: (name: string, rows: []string, want_count: s64) {
     t.expect(m.count() == want_count, name);
 }
 
-main :: () -> s32 {
+main :: () -> i32 {
     // Single horizontal 3-run (row 3, cols 2-4).
     scene("horizontal-3", .[
         "OGOGOGOG",
diff --git a/tests/refill.sx b/tests/refill.sx
index de3022c..75fcfef 100644
--- a/tests/refill.sx
+++ b/tests/refill.sx
@@ -41,8 +41,8 @@ load_board :: (rows: []string) -> Board {
     b
 }
 
-count_empties :: (b: *Board) -> s64 {
-    n : s64 = 0;
+count_empties :: (b: *Board) -> i64 {
+    n : i64 = 0;
     for 0..BOARD_CELLS (i) { if b.cells[i] == .empty { n += 1; } }
     n
 }
@@ -72,7 +72,7 @@ fresh_board :: () -> Board {
     b
 }
 
-main :: () -> s32 {
+main :: () -> i32 {
     print("== refill (seeded) ==\n");
 
     // Pipeline, snapshotting each stage.
@@ -123,7 +123,7 @@ main :: () -> s32 {
     // filled, then refill again. The board's RNG has advanced past the first
     // fill, so the second fill draws new gems — proof it does NOT reseed per call.
     holes_n := 0;
-    hole_idx : [BOARD_CELLS]s64 = ---;
+    hole_idx : [BOARD_CELLS]i64 = ---;
     fill1 : [BOARD_CELLS]Gem = ---;
     for 0..BOARD_CELLS (i) {
         if pre.cells[i] == .empty {
diff --git a/tests/score.sx b/tests/score.sx
index 0c956da..e0e7427 100644
--- a/tests/score.sx
+++ b/tests/score.sx
@@ -42,7 +42,7 @@ load_board :: (rows: []string) -> Board {
 
 // Score one scene: snapshot board + enumerated runs + points, then assert
 // `score_round` is exact and `add_round_score` accumulates it into `board.score`.
-scene :: (name: string, rows: []string, want_points: s64) {
+scene :: (name: string, rows: []string, want_points: i64) {
     b := load_board(rows);
     runs := find_runs(@b);
 
@@ -58,7 +58,7 @@ scene :: (name: string, rows: []string, want_points: s64) {
              concat(name, ": add_round_score accumulates into board.score"));
 }
 
-main :: () -> s32 {
+main :: () -> i32 {
     print("== score (base match scoring) ==\n");
 
     // Single length-3 horizontal run (row 3, cols 2-4) -> SCORE_RUN_3 = 30.
diff --git a/tests/swap_legality.sx b/tests/swap_legality.sx
index 5548031..1cd94da 100644
--- a/tests/swap_legality.sx
+++ b/tests/swap_legality.sx
@@ -44,11 +44,11 @@ boards_equal :: (x: *Board, y: *Board) -> bool {
     true
 }
 
-cell :: (col: s64, row: s64) -> Cell {
+cell :: (col: i64, row: i64) -> Cell {
     Cell.{ col = col, row = row }
 }
 
-main :: () -> s32 {
+main :: () -> i32 {
     print("== swap & legality ==\n");
 
     // Board whose ONLY swap-formable match is the adjacent (2,3)<->(3,3)
diff --git a/tests/swipe_commit.sx b/tests/swipe_commit.sx
index 19154d3..eb8aa47 100644
--- a/tests/swipe_commit.sx
+++ b/tests/swipe_commit.sx
@@ -20,7 +20,7 @@
 
 SEED :: 1337;
 
-cell_center :: (lay: *BoardLayout, col: s64, row: s64) -> Point {
+cell_center :: (lay: *BoardLayout, col: i64, row: i64) -> Point {
     cf := lay.cell_frame(col, row);
     Point.{ x = cf.mid_x(), y = cf.mid_y() }
 }
@@ -32,14 +32,14 @@ boards_equal :: (x: *Board, y: *Board) -> bool {
     true
 }
 
-main :: () -> s32 {
+main :: () -> i32 {
     // 800×600, no safe inset → 600px square grid, cell 75, origin (100, 0). A
     // 60px drag clears the cell*0.5 = 37.5px swipe threshold on the dominant axis.
     lay : BoardLayout = ---;
     lay.compute(Frame.make(0.0, 0.0, 800.0, 600.0), EdgeInsets.zero());
     D : f32 = 60.0;
 
-    fails : s64 = 0;
+    fails : i64 = 0;
 
     // ── ILLEGAL swipe reverts ──────────────────────────────────────────────
     // (0,0) and (1,0) are both red on the seed board, so swapping them forms no
diff --git a/tests/swipe_intent.sx b/tests/swipe_intent.sx
index f83f423..faf19c6 100644
--- a/tests/swipe_intent.sx
+++ b/tests/swipe_intent.sx
@@ -14,14 +14,14 @@
 #import "board_layout.sx";
 #import "swipe.sx";
 
-cell_center :: (lay: *BoardLayout, col: s64, row: s64) -> Point {
+cell_center :: (lay: *BoardLayout, col: i64, row: i64) -> Point {
     cf := lay.cell_frame(col, row);
     Point.{ x = cf.mid_x(), y = cf.mid_y() }
 }
 
 // Print the resolved intent (locked in the golden) and report whether it matches
 // the expected adjacent pair (A, B). Drives the exit code alongside the dump.
-expect_swap :: (label: string, got: ?Swap, ac: s64, ar: s64, bc: s64, br: s64) -> bool {
+expect_swap :: (label: string, got: ?Swap, ac: i64, ar: i64, bc: i64, br: i64) -> bool {
     if s := got {
         print("{}: ({},{})->({},{})\n", label, s.a.col, s.a.row, s.b.col, s.b.row);
         return s.a.col == ac and s.a.row == ar and s.b.col == bc and s.b.row == br;
@@ -39,14 +39,14 @@ expect_none :: (label: string, got: ?Swap) -> bool {
     true
 }
 
-main :: () -> s32 {
+main :: () -> i32 {
     lay : BoardLayout = ---;
     lay.compute(Frame.make(0.0, 0.0, 800.0, 600.0), EdgeInsets.zero());
     print("grid origin ({},{}) cell {} threshold {}\n",
-        cast(s64) lay.origin.x, cast(s64) lay.origin.y, cast(s64) lay.cell_size,
-        cast(s64) (lay.cell_size * SWIPE_THRESHOLD_FRACTION));
+        cast(i64) lay.origin.x, cast(i64) lay.origin.y, cast(i64) lay.cell_size,
+        cast(i64) (lay.cell_size * SWIPE_THRESHOLD_FRACTION));
 
-    fails : s64 = 0;
+    fails : i64 = 0;
 
     // A known interior cell; every cardinal swipe from it stays on the board.
     start := cell_center(@lay, 3, 5);
diff --git a/tests/swipe_reshuffle.sx b/tests/swipe_reshuffle.sx
index 0834634..975cfa7 100644
--- a/tests/swipe_reshuffle.sx
+++ b/tests/swipe_reshuffle.sx
@@ -36,7 +36,7 @@ char_to_gem :: (c: u8) -> Gem {
 
 // Load an 8x8 board from `rows` (top row first), seeded RNG, score zeroed, turn
 // counters reset to a fresh game, and the per-level goal set.
-load_board :: (rows: []string, seed: s64, move_limit: s64, target_score: s64) -> Board {
+load_board :: (rows: []string, seed: i64, move_limit: i64, target_score: i64) -> Board {
     b : Board = ---;
     for 0..BOARD_ROWS (row) {
         line := rows[row];
@@ -52,13 +52,13 @@ load_board :: (rows: []string, seed: s64, move_limit: s64, target_score: s64) ->
     b
 }
 
-cell_center :: (lay: *BoardLayout, col: s64, row: s64) -> Point {
+cell_center :: (lay: *BoardLayout, col: i64, row: i64) -> Point {
     cf := lay.cell_frame(col, row);
     Point.{ x = cf.mid_x(), y = cf.mid_y() }
 }
 
-main :: () -> s32 {
-    fails : s64 = 0;
+main :: () -> i32 {
+    fails : i64 = 0;
 
     // 800×600, no safe inset → 600px square grid, cell 75, origin (100, 0). A 60px
     // drag clears the cell*0.5 = 37.5px swipe threshold on the dominant axis — the
diff --git a/tests/turn.sx b/tests/turn.sx
index 0db53ee..d6d25bf 100644
--- a/tests/turn.sx
+++ b/tests/turn.sx
@@ -37,7 +37,7 @@ char_to_gem :: (c: u8) -> Gem {
 // Load an 8x8 board from `rows` (top row first, each exactly BOARD_COLS chars),
 // seeded RNG, running score zeroed, and the turn counters reset to a fresh game
 // (no moves made, the given move budget).
-load_board :: (rows: []string, seed: s64, move_limit: s64) -> Board {
+load_board :: (rows: []string, seed: i64, move_limit: i64) -> Board {
     b : Board = ---;
     for 0..BOARD_ROWS (row) {
         line := rows[row];
@@ -60,7 +60,7 @@ boards_equal :: (a: *Board, b: *Board) -> bool {
 // One flag scene: snapshot the board, then count its single round's special
 // runs and assert the tallies (and the boolean flags derived from them) are
 // exactly the documented values. No RNG, no clear — pure detection.
-flag_scene :: (name: string, rows: []string, want_len4: s64, want_len5_plus: s64) {
+flag_scene :: (name: string, rows: []string, want_len4: i64, want_len5_plus: i64) {
     print("== {} ==\n", name);
     b := load_board(rows, 0, LIMIT);
     out(board_dump(@b));
@@ -71,7 +71,7 @@ flag_scene :: (name: string, rows: []string, want_len4: s64, want_len5_plus: s64
     t.expect(sp.len5_plus == want_len5_plus, concat(name, ": len5_plus count exact"));
 }
 
-main :: () -> s32 {
+main :: () -> i32 {
     print("== turn (accounting + special-match flagging) ==\n");
 
     // ── Special-match flagging (single round, no RNG) ──────────────────────
diff --git a/tools/key_particle.sx b/tools/key_particle.sx
index 459c470..4bd5565 100644
--- a/tools/key_particle.sx
+++ b/tools/key_particle.sx
@@ -33,14 +33,14 @@ GRAY_TOL    :: 24;     // max channel spread still considered neutral gray
 LUM_MARGIN  :: 4;      // lum headroom above the light checker shade
 
 is_gray :: (r: u8, g: u8, b: u8) -> bool {
-    hi := max(max(cast(s64) r, cast(s64) g), cast(s64) b);
-    lo := min(min(cast(s64) r, cast(s64) g), cast(s64) b);
+    hi := max(max(cast(i64) r, cast(i64) g), cast(i64) b);
+    lo := min(min(cast(i64) r, cast(i64) g), cast(i64) b);
     hi - lo <= GRAY_TOL
 }
 
 // Mark pixel `i` as removed background and queue it, if it is unvisited checker
 // (near-neutral gray no brighter than the light checker shade + margin).
-fd_seed :: (i: s64, bg: [*]u8, lum: [*]s64, src: [*]u8, stack: [*]s64, sp: *s64, lim: s64) {
+fd_seed :: (i: i64, bg: [*]u8, lum: [*]i64, src: [*]u8, stack: [*]i64, sp: *i64, lim: i64) {
     if bg[i] != 0 { return; }
     p := i * 4;
     if lum[i] <= lim and is_gray(src[p], src[p+1], src[p+2]) {
@@ -50,35 +50,35 @@ fd_seed :: (i: s64, bg: [*]u8, lum: [*]s64, src: [*]u8, stack: [*]s64, sp: *s64,
     }
 }
 
-main :: () -> s32 {
-    w : s32 = 0;
-    h : s32 = 0;
-    ch : s32 = 0;
+main :: () -> i32 {
+    w : i32 = 0;
+    h : i32 = 0;
+    ch : i32 = 0;
     src : [*]u8 = xx stbi_load(SRC_PATH, @w, @h, @ch, 4);
     if xx src == 0 {
         print("FATAL: could not load {}\n", SRC_PATH);
         return 1;
     }
-    W := cast(s64) w;
-    H := cast(s64) h;
+    W := cast(i64) w;
+    H := cast(i64) h;
     N := W * H;
     print("loaded {}x{} ({} src channels)\n", w, h, ch);
 
     // Hoisted working locals (see codegen note above).
-    y : s64 = 0;
-    x : s64 = 0;
-    i : s64 = 0;
-    p : s64 = 0;
-    r : s64 = 0;
-    g : s64 = 0;
-    b : s64 = 0;
-    l : s64 = 0;
+    y : i64 = 0;
+    x : i64 = 0;
+    i : i64 = 0;
+    p : i64 = 0;
+    r : i64 = 0;
+    g : i64 = 0;
+    b : i64 = 0;
+    l : i64 = 0;
 
     // Per-pixel luminance, plus the checker shades read off the border ring
     // (the border is pure checker — the glow never reaches the corners).
-    lum : [*]s64 = xx context.allocator.alloc_bytes(N * size_of(s64));
-    c_lo : s64 = 255;
-    c_hi : s64 = 0;
+    lum : [*]i64 = xx context.allocator.alloc_bytes(N * size_of(i64));
+    c_lo : i64 = 255;
+    c_hi : i64 = 0;
     y = 0;
     while y < H {
         x = 0;
@@ -104,8 +104,8 @@ main :: () -> s32 {
     // border pixel. `bg[i]==1` marks a removed (transparent) background pixel.
     bg : [*]u8 = xx context.allocator.alloc_bytes(N);
     memset(xx bg, 0, N);
-    stack : [*]s64 = xx context.allocator.alloc_bytes(N * size_of(s64));
-    sp : s64 = 0;
+    stack : [*]i64 = xx context.allocator.alloc_bytes(N * size_of(i64));
+    sp : i64 = 0;
     checker_lim := c_hi + LUM_MARGIN;
 
     x = 0;
@@ -121,12 +121,12 @@ main :: () -> s32 {
         y += 1;
     }
 
-    cx : s64 = 0;
-    cy : s64 = 0;
-    dx : s64 = 0;
-    dy : s64 = 0;
-    nx : s64 = 0;
-    ny : s64 = 0;
+    cx : i64 = 0;
+    cy : i64 = 0;
+    dx : i64 = 0;
+    dy : i64 = 0;
+    nx : i64 = 0;
+    ny : i64 = 0;
     while sp > 0 {
         sp -= 1;
         i = stack[sp];
@@ -154,8 +154,8 @@ main :: () -> s32 {
     denom := cast(f32) (255 - c_hi);
     if denom < 1.0 { denom = 1.0; }
     alpha : [*]f32 = xx context.allocator.alloc_bytes(N * size_of(f32));
-    kept : s64 = 0;
-    n_bg : s64 = 0;
+    kept : i64 = 0;
+    n_bg : i64 = 0;
     a : f32 = 0.0;
     i = 0;
     while i < N {
@@ -178,26 +178,26 @@ main :: () -> s32 {
     sxf := cast(f32) W / cast(f32) OUT_DIM;
     syf := cast(f32) H / cast(f32) OUT_DIM;
     max_a : f32 = 0.0;
-    ty : s64 = 0;
-    tx : s64 = 0;
-    x0 : s64 = 0;
-    x1 : s64 = 0;
-    y0 : s64 = 0;
-    y1 : s64 = 0;
+    ty : i64 = 0;
+    tx : i64 = 0;
+    x0 : i64 = 0;
+    x1 : i64 = 0;
+    y0 : i64 = 0;
+    y1 : i64 = 0;
     sum : f32 = 0.0;
-    cnt : s64 = 0;
-    sy : s64 = 0;
-    sx : s64 = 0;
+    cnt : i64 = 0;
+    sy : i64 = 0;
+    sx : i64 = 0;
     av : f32 = 0.0;
-    o : s64 = 0;
+    o : i64 = 0;
     ty = 0;
     while ty < OUT_DIM {
         tx = 0;
         while tx < OUT_DIM {
-            x0 = cast(s64) (cast(f32) tx * sxf);
-            x1 = cast(s64) (cast(f32) (tx + 1) * sxf);
-            y0 = cast(s64) (cast(f32) ty * syf);
-            y1 = cast(s64) (cast(f32) (ty + 1) * syf);
+            x0 = cast(i64) (cast(f32) tx * sxf);
+            x1 = cast(i64) (cast(f32) (tx + 1) * sxf);
+            y0 = cast(i64) (cast(f32) ty * syf);
+            y1 = cast(i64) (cast(f32) (ty + 1) * syf);
             if x1 <= x0 { x1 = x0 + 1; }
             if y1 <= y0 { y1 = y0 + 1; }
             sum = 0.0;