P11.3: glossier candy gem & selection feel (sx / iOS)

Make the selection highlight read as glossy candy without new art and
without disturbing the idle-rest invariant. board_view's render_selection
layers a soft outward glow (two concentric stroked rings — the renderer has
no blur), a warm wash, a bright rim doubled by a thin inner highlight for a
glassy edge, and a wet sheen that rides the selected gem's live pose. Every
layer is a rect/overlay (issue 0002 forbids a draw-time gem-texture tint).

The gloss is selection-only: render_selection runs solely when a cell is
selected, so the resting board (no selection) is byte-identical to before
and the t==0 idle pose stays exactly the static sprite (locked by
tests/gem_pose). The selection-pop motion still comes from gem_anim; no
board / score / move state changes and input stays gated by BoardAnim.active.

Updated goldens/p6_select.png; README documents the P11.3 selection gloss
and its reproduce commands (reusing the P6.3 M3TE_SELECT + M3TE_ANIM_TIME
hooks).

README.md

@@ -172,3 +172,28 @@ env SIMCTL_CHILD_M3TE_FX=11 SIMCTL_CHILD_M3TE_ANIM_TIME=3.0 \
 
 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:
+
+```bash
+# 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.

board_view.sx

@@ -33,11 +33,18 @@ GEM_FILL_FRAC :f32: 0.84;
 // actually sizes it; vertical centering inside the safe area is unchanged.
 BOARD_INSET_X :f32: 16.0;
 
-// Selection overlay: a translucent warm fill plus a bright opaque rim around the
-// chosen cell. `add_stroked_rect` draws the rim in its FILL color (the renderer
-// ignores the separate stroke color), so SELECT_RIM is passed as the fill.
-SELECT_FILL :: Color.{ r = 255, g = 240, b = 120, a = 70 };
-SELECT_RIM  :: Color.{ r = 255, g = 228, b = 60,  a = 255 };
+// Selection overlay (P11.3): a soft candy "glow" halo, a warm wash over the cell,
+// a bright rim topped by a glossy inner highlight, and a wet sheen on the chosen
+// gem. `add_stroked_rect` paints the border band in its FILL colour (the shader
+// ignores the separate stroke colour), so each ring colour is passed as the fill.
+// The engine can't tint/fade a texture at draw time (issue 0002), so every layer
+// here is a rect/overlay — never a gem-texture tint.
+SELECT_GLOW_OUT :: Color.{ r = 255, g = 232, b = 140, a = 30 };  // wide faint outer bloom
+SELECT_GLOW_IN  :: Color.{ r = 255, g = 238, b = 150, a = 70 };  // brighter near-edge halo
+SELECT_FILL     :: Color.{ r = 255, g = 244, b = 150, a = 80 };  // warm wash over the gem
+SELECT_RIM      :: Color.{ r = 255, g = 234, b = 92,  a = 255 }; // bright candy rim
+SELECT_RIM_HI   :: Color.{ r = 255, g = 255, b = 232, a = 220 }; // glossy inner highlight ring
+SELECT_GLOSS    :: Color.{ r = 255, g = 255, b = 255, a = 96 };  // wet sheen on the selected gem
 
 // HUD: a translucent card with the score and remaining moves, in the loaded Lato
 // font. Placed in the empty band above the centered grid (inside the safe area).
@@ -302,6 +309,39 @@ BoardView :: struct {
         }
     }
 
+    // Selection emphasis (P11.3): a glossier candy highlight on the chosen cell.
+    // Two concentric stroked rings fake a soft outward glow (the renderer has no
+    // blur), 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. All rect/overlay layers (issue 0002 forbids a draw-time gem tint); the
+    // selection-pop motion still comes from gem_anim, so the t==0 idle pose is
+    // untouched.
+    render_selection :: (self: *BoardView, ctx: *RenderContext, dim: f32) {
+        cs := self.layout.cell_size;
+        cf := self.layout.cell_frame(self.sel.cell.col, self.sel.cell.row);
+
+        // Glow halo: rings just outside the cell edge, brighter nearer the rim, so
+        // the falloff reads as a soft bloom without tinting the gem interior.
+        ctx.add_stroked_rect(cf.expand(cs * 0.16), SELECT_GLOW_OUT, SELECT_GLOW_OUT, cs * 0.16, cs * 0.30);
+        ctx.add_stroked_rect(cf.expand(cs * 0.07), SELECT_GLOW_IN,  SELECT_GLOW_IN,  cs * 0.08, cs * 0.21);
+
+        // Warm wash + bright rim + a thin glossy highlight ring just inside the rim.
+        ctx.add_rounded_rect(cf, SELECT_FILL, cs * 0.14);
+        rim_w := max(2.0, cs * 0.06);
+        ctx.add_stroked_rect(cf, SELECT_RIM, SELECT_RIM, rim_w, cs * 0.14);
+        hi_w := max(1.0, cs * 0.022);
+        ctx.add_stroked_rect(cf.expand(0.0 - rim_w), SELECT_RIM_HI, SELECT_RIM_HI, hi_w, cs * 0.11);
+
+        // Wet sheen on the selected gem: a bright pill in its upper third, sized to
+        // the gem's live pose so it tracks the selection pop.
+        pose := self.gem_pose_at(self.sel.cell.col, self.sel.cell.row);
+        gf := self.gem_pose_frame(self.sel.cell.col, self.sel.cell.row, dim, pose);
+        gw := gf.size.width;
+        gh := gf.size.height;
+        gloss := Frame.make(gf.origin.x + gw * 0.22, gf.origin.y + gh * 0.13, gw * 0.40, gh * 0.22);
+        ctx.add_rounded_rect(gloss, SELECT_GLOSS, gh * 0.12);
+    }
+
     // Play the active slice of the move timeline. Gem motion is clipped to the
     // grid so refilled gems slide in from behind the top edge rather than
     // overlapping the HUD band above the board.
@@ -582,13 +622,10 @@ impl View for BoardView {
             }
         }
 
-        // 3. Selection overlay on the chosen cell: a translucent fill under a
-        //    bright rim, drawn over the whole grid so it reads as a highlight.
+        // 3. Selection emphasis on the chosen cell: a soft candy glow halo under a
+        //    warm wash, a bright glossy rim, and a wet sheen on the popped gem.
         if self.sel != null and self.sel.active {
-            cf := self.layout.cell_frame(self.sel.cell.col, self.sel.cell.row);
-            ctx.add_rect(cf, SELECT_FILL);
-            rim_w := max(2.0, self.layout.cell_size * 0.06);
-            ctx.add_stroked_rect(cf, SELECT_RIM, SELECT_RIM, rim_w, self.layout.cell_size * 0.14);
+            self.render_selection(ctx, gem_dim);
         }
 
         // 4. HUD card with score + remaining moves, in the band above the grid.