Game logic, rendering, input, and UI are all authored in sx.
Art (palettes, sprite sheets) is produced as real assets.
Verification gate: sx logic tests pass AND the iOS app builds & launches in the Simulator.

Development is driven by the multi-agent flow (Product Owner → Worker → Reviewer → Observer).

Verification gate

The gate has two halves. Both must pass. The sx compiler used below lives at /Users/agra/projects/sx/zig-out/bin/sx (override the runner's binary with the SX env var). Run everything from the repo root.

1. Logic tests

Pure-sx logic tests run under sx and have their stdout + exit code diffed against committed snapshots in tests/expected/. A failed assertion exits the process non-zero, so it fails the runner (and the gate).

bash tools/run_tests.sh

A test is any tests/<name>.sx that has a tests/expected/<name>.exit marker; tests/test.sx (the expect assert helper) has no marker, so it is not itself run.
Regenerate snapshots after an intentional change: bash tools/run_tests.sh --update.

2. iOS Simulator build + launch

Build the app for the simulator, then install/launch it on an available device and screenshot the rendered scene (blue background + a centered orange quad).

# Build the .app bundle (sx-out/ios/M3te.app):
/Users/agra/projects/sx/zig-out/bin/sx build --target ios-sim main.sx

# Discover an available simulator — do NOT hardcode a udid:
xcrun simctl list devices available
# e.g. capture the first available device's UDID into $udid:
udid=$(xcrun simctl list devices available | grep -Eo '[0-9A-Fa-f-]{36}' | head -1)

# Boot it (skip if already "Booted") and bring the Simulator window up:
xcrun simctl boot "$udid" || true
open -a Simulator

# Install, launch (bundle id co.swipelab.m3te), and screenshot:
xcrun simctl install booted sx-out/ios/M3te.app
xcrun simctl launch booted co.swipelab.m3te
xcrun simctl io booted screenshot /tmp/m3te.png

The screenshot should match goldens/p0_quad.png (a centered orange quad over a blue clear), modulo the status-bar clock — pixel-exact equality is not required. A tap on the quad flips its color (orange ↔ green); see goldens/p0_input_before.png / goldens/p0_input_after.png.

Deterministic animation capture (P6.3)

The per-gem idle loop (gem_anim.sx) is always-on, so a plain screenshot is time-dependent. Two environment variables pin the visual state so the board can be captured reproducibly. The simulator forwards any SIMCTL_CHILD_* variable to the launched app, so prefix them on the simctl launch:

M3TE_ANIM_TIME=<seconds> freezes the animation clock at that phase. t=0 is the resting board — every gem sits at its static pose, so the pre-P6.3 goldens reproduce unchanged. A larger t (e.g. 1.0) shows the mid-breath idle deformation. The select/land reactions read this same pinned phase.
M3TE_SELECT=<cellIndex 0..63> (= row*8 + col) force-selects a cell at startup, so the selection highlight + pop can be captured without a tap.

# Resting board (idle at rest): goldens/p6_idle_t0.png
SIMCTL_CHILD_M3TE_ANIM_TIME=0   xcrun simctl launch booted co.swipelab.m3te
# Mid-breath idle: goldens/p6_idle_mid.png
SIMCTL_CHILD_M3TE_ANIM_TIME=1.0 xcrun simctl launch booted co.swipelab.m3te
# Selection pop on cell (3,3): goldens/p6_select.png
env SIMCTL_CHILD_M3TE_ANIM_TIME=0.17 SIMCTL_CHILD_M3TE_SELECT=27 \
    xcrun simctl launch booted co.swipelab.m3te

With no variable set the game runs fully live (the clock advances by delta_time). tests/gem_pose.sx locks the t==0-rest invariant headlessly.

Level-state capture (P7.2)

The win/lose banner and restart button are driven by the model's level_status (score vs. goal vs. move budget). Three more env hooks force a terminal status (or a restart) so the banner / restart states can be screenshot deterministically without scripting a winning swipe — combine them with M3TE_ANIM_TIME to pin the idle clock:

M3TE_TARGET=<n> overrides the per-level score goal. 0 makes the fresh board read won immediately (score 0 ≥ goal 0).
M3TE_MOVE_LIMIT=<n> overrides the move budget. 0 makes it read lost (budget spent below the goal).
M3TE_RESTART=<non-zero> runs board.restart after the overrides, capturing the fresh in_progress board the restart button produces.

# Win banner + restart over the board: goldens/p7_win.png
env SIMCTL_CHILD_M3TE_TARGET=0 SIMCTL_CHILD_M3TE_ANIM_TIME=0 \
    xcrun simctl launch booted co.swipelab.m3te
# Lose banner ("OUT OF MOVES") + restart: goldens/p7_lose.png
env SIMCTL_CHILD_M3TE_MOVE_LIMIT=0 SIMCTL_CHILD_M3TE_ANIM_TIME=0 \
    xcrun simctl launch booted co.swipelab.m3te
# Fresh in_progress board after restart: goldens/p7_restart.png
env SIMCTL_CHILD_M3TE_TARGET=0 SIMCTL_CHILD_M3TE_RESTART=1 SIMCTL_CHILD_M3TE_ANIM_TIME=0 \
    xcrun simctl launch booted co.swipelab.m3te

While a banner is up the board freezes (only the restart button is live, per P7.1's finished-level rule); tests/banner_layout.sx locks the restart button's rect ↔ hit-test round-trip headlessly.

Match-FX capture (P11.1)

The match bursts + score popup (board_fx.sx) only spawn off a committed move, which the simulator can't script (there is no public touch injection). One more env hook forces a representative match at startup so the FX can be screenshot deterministically — combine it with M3TE_ANIM_TIME to freeze the phase:

M3TE_FX=<n> commits the n-th currently-legal swap (1-based, clamped; =1 is the first) through the normal plan_and_commit path, then begins the move timeline + its burst/popup FX. While M3TE_ANIM_TIME is set the move/FX timelines are pinned at that phase (the frame loop holds them frozen), so the burst and floating +points render identically every run. A larger M3TE_ANIM_TIME lands past the timeline, capturing the settled board with the FX fully pruned. Startup-only and guarded by the var, so normal play is untouched.

The legal-swap order is the fixed enumeration in tests/expected/swap_legality.stdout (row-major, right-before-down). For seed 1337, M3TE_FX=3 is the vertical red 3-match used by the golden, and M3TE_FX=11 is a depth-5 cascade (the deepest on this seed) used to capture the escalated combo emphasis (next section).

# Punchy match burst + "+30" popup, pinned mid-clear: goldens/p6_fx_match.png
env SIMCTL_CHILD_M3TE_FX=3 SIMCTL_CHILD_M3TE_ANIM_TIME=0.22 \
    xcrun simctl launch booted co.swipelab.m3te
# Same match, later phase — FX fully gone over the settled board (no golden):
env SIMCTL_CHILD_M3TE_FX=3 SIMCTL_CHILD_M3TE_ANIM_TIME=2.0 \
    xcrun simctl launch booted co.swipelab.m3te

Escalating combo emphasis (P11.2)

The combo FX escalates with cascade depth (mv.rounds.len), the SAME depth the cascade SFX (play_cascade) steps up on: a deeper cascade gets a bigger, hotter- gold +points popup topped by a COMBO xN label, and bursts that grow from the first round. The depth→emphasis clamp (fx_combo_level) mirrors the cascade cue's cascade_cue_index exactly (depth ≤ 1 → floor, depth ≥ 5 → ceiling); the equivalence is locked headlessly by tests/fx_combo.sx.

Capture it with the same M3TE_FX hook — M3TE_FX=11 is a depth-5 cascade on seed 1337, contrasted against the depth-1 single clear M3TE_FX=3:

# Escalated COMBO x5 + gold "+1050" + bigger burst: goldens/p11_combo_deep.png
env SIMCTL_CHILD_M3TE_FX=11 SIMCTL_CHILD_M3TE_ANIM_TIME=0.22 \
    xcrun simctl launch booted co.swipelab.m3te
# Single clear for contrast — plain white "+30", no COMBO label (goldens/p6_fx_match.png):
env SIMCTL_CHILD_M3TE_FX=3 SIMCTL_CHILD_M3TE_ANIM_TIME=0.22 \
    xcrun simctl launch booted co.swipelab.m3te
# Deep cascade at a later phase — all combo FX gone over the settled board (no golden):
env SIMCTL_CHILD_M3TE_FX=11 SIMCTL_CHILD_M3TE_ANIM_TIME=3.0 \
    xcrun simctl launch booted co.swipelab.m3te

The combo emphasis is purely visual and self-pruning: it never gates input (BoardAnim.active owns gating) and never touches board / score / move state.

Glossier gem & selection feel (P11.3)

The selection highlight (board_view.sx render_selection) is a candy-glossier overlay: two concentric stroked rings fake a soft outward glow, a warm wash tints the cell, a bright rim is doubled by a thin inner highlight for a glassy edge, and a wet sheen rides the selected gem's live pose. The engine can't tint a texture at draw time (issue 0002), so every layer is a rect/overlay — never a gem-texture tint. The selection-pop motion still comes from gem_anim, so the t==0 idle pose is byte-identical to the static sprite (locked by tests/gem_pose.sx); the gloss is selection-only, so the resting board (no selection) is unchanged.

Capture it with the same P6.3 hooks — no new env var:

# Glossy candy selection on cell (3,3), pinned mid-pop: goldens/p6_select.png
env SIMCTL_CHILD_M3TE_ANIM_TIME=0.17 SIMCTL_CHILD_M3TE_SELECT=27 \
    xcrun simctl launch booted co.swipelab.m3te
# Same selection at exact rest (no pop) — isolates the overlay:
env SIMCTL_CHILD_M3TE_ANIM_TIME=0 SIMCTL_CHILD_M3TE_SELECT=27 \
    xcrun simctl launch booted co.swipelab.m3te

The selection gloss is purely visual: it never gates input (BoardAnim.active owns gating) and never touches board / score / move state.