Merge feat/blend-transparency: colorkey + per-object alpha/tint blend (graphics slice A)

Fixes the SC0000 opening's opaque grey-wall: layers now alpha-blend and honor
per-surface colorkey. Hybrid arch (engine resolves RenderObject blend plan,
Godot host blits). Deferred: smooth color-anim interpolation + additive/glow.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/opcode-reference.md

@@ -102,12 +102,12 @@ Native handler sleep_op_0xc8 @0x420ec0 is NON-BLOCKING: it arms a timer (sleep_t
 - **evidence:** Ghidra handler 0x4227b0 (dispatch ctx[0x26c93+0x1ff]); FUN_0047e800(op1,(float)op2,(float)op3,(float)op4).
 
 ### 0x202 `gfx-blit-color` (gfx-blit-color, argc 5)
-- **summary:** 0x202 (handle)(x)(y)(alpha)(color) — gfx cmd-type 0xb. Handler gfx_op_0x202_blit_color @0x4228d0: blits object `handle` at (x,y) with a packed ARGB built from alpha(op4, ≥0x100→0xff, <0→FUN_0047f3e0) and color(op5, <0→FUN_0047f3e0) → FUN_0047ea00. See docs/engine-re.md gfx op-contract table.
+- **summary:** 0x202 (handle)(x)(y)(alpha)(color) — gfx cmd-type 0xb. Handler gfx_op_0x202_blit_color @0x4228d0: worker gfx_op_0x202_worker_set_color_anim @0x47ea00 sets an ANIMATED color/alpha target (obj+0x64) + anim bit; packs ARGB from alpha(op4, ≥0x100→0xff, <0→FUN_0047f3e0) and color(op5, <0→FUN_0047f3e0). C# VM (2026-07-08 blend slice): routes through GfxState.SetObjectColor → the compositor applies STATIC alpha/tint (BlendKind.Alpha); smooth color-anim interpolation deferred. See docs/engine-re.md §Blend & transparency.
 - **grounding:** source=investigation, confidence=high
 - **evidence:** Ghidra handler 0x4228d0 (dispatch ctx[0x26c93+0x202]); packs (alpha<<24|rgb) from operands 4/5, FUN_0047ea00(op1,op2,op3,packed).
 
 ### 0x203 `gfx-draw-color` (gfx-draw-color, argc 4)
-- **summary:** 0x203 (handle)(v)(alpha)(color) — gfx cmd-type 9. Handler gfx_op_0x203_draw_color @0x4229a0: draws object `handle` with op2 + a packed ARGB from alpha(op3)/color(op4) → FUN_0047e9b0. Sibling of 0x202 with one fewer positional arg. See docs/engine-re.md gfx op-contract table.
+- **summary:** 0x203 (handle)(v)(alpha)(color) — gfx cmd-type 9. Handler gfx_op_0x203_draw_color @0x4229a0: worker gfx_op_0x203_worker_set_color @0x47e9b0 sets a STATIC color/alpha (obj+0x60), no anim bit; packs ARGB from alpha(op3)/color(op4). Sibling of 0x202 (one fewer positional arg). C# VM (2026-07-08 blend slice): routes through GfxState.SetObjectColor → compositor applies static alpha/tint (BlendKind.Alpha). See docs/engine-re.md §Blend & transparency.
 - **grounding:** source=investigation, confidence=high
 - **evidence:** Ghidra handler 0x4229a0 (dispatch ctx[0x26c93+0x203]); packs color from operands 3/4, FUN_0047e9b0(op1,op2,packed).
 

docs/phase-a-slice-plan.md

@@ -600,3 +600,32 @@ compositing + cold-object anchors (the thing that makes the paced opening actual
 the Ctrl `Speed` multiplier (ADV-mode-scope RE). (c) Full scene-coroutine framework (`0x7b`/`0x7c`/`0x140`)
 for interactive multi-object scenes. (d) Model `0xcd get-input-type` (name-entry interactivity, the separate
 input gap noted above).
+
+### A2b — Blend & transparency (slice A) ✅ DONE (2026-07-08)
+
+First of three graphics-fidelity slices (A blend/transparency, B geometry/anchors, C render-targets).
+Spec `docs/superpowers/specs/2026-07-08-blend-transparency-design.md`, plan
+`docs/superpowers/plans/2026-07-08-blend-transparency.md`, branch `feat/blend-transparency` (engine 69/69,
+sweep exit=284/STEP-LIMIT=13 parity, `SELFTEST OK`).
+
+**Landed (hybrid: engine resolves, host blits):**
+- `Age.Engine/Model/BlendMath.cs` — pure colorkey match + ARGB unpack (colorkey format reversed:
+  op arg 3 `<0` = none, else `0xRRGGBB` exact-match, `0` = key black; baked at surface-load, see
+  engine-re.md §Blend).
+- `RenderObject` gains `Alpha`/`Tint`/`Blend` (`BlendKind` Opaque|Alpha|Additive); `GfxObject.HasColor`;
+  `GfxState.SetObjectColor`; `SnapshotVisibleObjects` resolves them. `0x202`/`0x203` route through
+  `SetObjectColor` (the stale "alpha deferred" trace stub is gone — alpha is now consumed).
+- Godot compositor: colorkey-baked image cache (keyed by `(path, colorKey)`), `BlitLayer` applies
+  colorkey + object alpha + RGB-tint modulate, and **surfaceless colored objects fill a tint×alpha quad**
+  (the fades) instead of being skipped.
+
+**Result (pixels):** page-1 event-CG composites cleanly (dialogue + prompt, no opaque boxes); the opening's
+mid-fade frames now alpha-blend (dark bg + light-ray burst, then a blended dark transition) instead of the
+pre-change **full-screen opaque grey wall** that ate the CG. Verified via `--shot`/`--shot-sequence` on
+`SC0000 --boot`.
+
+**Deferred (documented, NOT built — confirmed by a stalled interp RE pass, engine-re.md §Blend):**
+smooth color-animation *interpolation* (the fade ramps snap to the correct end-state rather than gliding —
+the `0x202` color channel's blit consumer + clock coupling is a dedicated dig) and **additive/glow blend**
+(`local_2c` mode 2/3; its object field isn't pinned). `BlendKind.Additive` is an unused seam. Next graphics
+slices unchanged: B (geometry/anchors — sprite *placement*) and C (render-targets).

engine/Age.Engine.Tests/BlendMathTests.cs

@@ -0,0 +1,34 @@
+using Age.Engine.Model;
+using Xunit;
+
+public class BlendMathTests
+{
+    [Fact]
+    public void NegativeColorKey_IsNoKey()
+    {
+        Assert.False(BlendMath.HasColorKey(-1));
+        Assert.False(BlendMath.ColorKeyMatches(0, 0, 0, -1));   // never matches when no key
+    }
+
+    [Fact]
+    public void ZeroColorKey_KeysBlack()
+    {
+        Assert.True(BlendMath.HasColorKey(0));
+        Assert.True(BlendMath.ColorKeyMatches(0, 0, 0, 0));      // (0,0,0) == key black
+        Assert.False(BlendMath.ColorKeyMatches(1, 0, 0, 0));    // near-black is NOT keyed (exact match)
+    }
+
+    [Fact]
+    public void ColorKey_MatchesRgb888Bytes()
+    {
+        long key = 0xFF00FF;                                    // magenta 0xRRGGBB
+        Assert.True(BlendMath.ColorKeyMatches(0xFF, 0x00, 0xFF, key));
+        Assert.False(BlendMath.ColorKeyMatches(0xFE, 0x00, 0xFF, key));
+    }
+
+    [Fact]
+    public void UnpackArgb_SplitsBytes()
+    {
+        Assert.Equal((0x80, 0x12, 0x34, 0x56), BlendMath.UnpackArgb(0x80123456));
+    }
+}

engine/Age.Engine.Tests/RenderObjectBlendTests.cs

@@ -0,0 +1,45 @@
+using System.Linq;
+using Age.Engine.Model;
+using Xunit;
+
+public class RenderObjectBlendTests
+{
+    // Make a visible textured object bound to a slot that has a surface, so it appears in the snapshot.
+    private static GfxState WithVisibleObject(long handle, long resId, long colorKey)
+    {
+        var g = new GfxState();
+        g.SetSurface(1, resId, colorKey);
+        g.BindDraw(handle, 1, 0, 0, 10, 10, 0, 0);   // draw-texture: slot 1, 10x10 at (0,0), visible
+        return g;
+    }
+
+    [Fact]
+    public void ObjectWithoutColor_ResolvesOpaqueWhiteTint()
+    {
+        var g = WithVisibleObject(0x100, resId: 5, colorKey: -1);
+        var ro = g.SnapshotVisibleObjects().Single();
+        Assert.Equal(255, ro.Alpha);
+        Assert.Equal(0xFFFFFF, ro.Tint);
+        Assert.Equal(BlendKind.Opaque, ro.Blend);
+    }
+
+    [Fact]
+    public void DrawColor_0x203_SetsAlphaTintAndBlend()
+    {
+        var g = WithVisibleObject(0x100, resId: 5, colorKey: -1);
+        // emulate op 0x203: pack (alpha=0x80, color=0x102030) and mark HasColor
+        g.SetObjectColor(0x100, GfxState.PackColor(0x80, 0x102030));
+        var ro = g.SnapshotVisibleObjects().Single();
+        Assert.Equal(0x80, ro.Alpha);
+        Assert.Equal(0x102030, ro.Tint);
+        Assert.Equal(BlendKind.Alpha, ro.Blend);
+    }
+
+    [Fact]
+    public void ColorKey_IsCarriedThrough()
+    {
+        var g = WithVisibleObject(0x100, resId: 5, colorKey: 0x000000);   // key black
+        var ro = g.SnapshotVisibleObjects().Single();
+        Assert.Equal(0x000000, ro.ColorKey);
+    }
+}

engine/Age.Engine/Model/BlendKind.cs

@@ -0,0 +1,6 @@
+namespace Age.Engine.Model;
+
+/// <summary>How an object's surface composites onto the canvas. Opaque = straight copy; Alpha = source-alpha
+/// blend (fades). Additive (glow/flash, native blit mode 2/3) is a documented seam — NOT implemented in the
+/// blend/transparency slice; see docs/superpowers/specs/2026-07-08-blend-transparency-design.md.</summary>
+public enum BlendKind { Opaque, Alpha, Additive }

engine/Age.Engine/Model/BlendMath.cs

@@ -0,0 +1,22 @@
+namespace Age.Engine.Model;
+
+/// <summary>Pure blend helpers shared by the engine resolution and the host blit. Colorkey semantics come
+/// from the native loader (docs/engine-re.md §"Blend & transparency"): op arg 3 &lt; 0 = no key; otherwise
+/// the operand is 0xRRGGBB and matching (R,G,B) texels are transparent (operand 0 = key black).</summary>
+public static class BlendMath
+{
+    /// <summary>A colorkey operand &gt;= 0 is an active key; a negative operand means "no colorkey".</summary>
+    public static bool HasColorKey(long colorKey) => colorKey >= 0;
+
+    /// <summary>True when (r,g,b) exactly equals the key's 0xRRGGBB bytes. Always false when there is no key.</summary>
+    public static bool ColorKeyMatches(byte r, byte g, byte b, long colorKey)
+    {
+        if (!HasColorKey(colorKey)) return false;
+        return r == ((colorKey >> 16) & 0xff) && g == ((colorKey >> 8) & 0xff) && b == (colorKey & 0xff);
+    }
+
+    /// <summary>Split a 0xAARRGGBB packed color (see GfxState.PackColor) into its byte channels.</summary>
+    public static (int A, int R, int G, int B) UnpackArgb(long packed)
+        => ((int)((packed >> 24) & 0xff), (int)((packed >> 16) & 0xff),
+            (int)((packed >> 8) & 0xff), (int)(packed & 0xff));
+}

engine/Age.Engine/Model/GfxState.cs

@@ -16,7 +16,7 @@ public readonly record struct AnimState(bool Enabled, bool Normalized, long TX,
 /// "The full gfx render model").</summary>
 public readonly record struct RenderObject(long Handle, long SurfaceResId, long ColorKey,
                                            int SrcX, int SrcY, int W, int H, int DstX, int DstY,
-                                           AnimState Anim);
+                                           AnimState Anim, int Alpha, long Tint, BlendKind Blend);
 
 /// <summary>Host-agnostic model of the AGE native gfx command-buffer (reversed in
 /// docs/engine-re.md, gfx op-contract table). One registry maps an object handle to a GfxObject — the
@@ -31,6 +31,7 @@ public sealed class GfxState
         public (long X, long Y, long Z) V18, V24, V16c;
         public long Field64, Field68, Field6c;
         public long Color;
+        public bool HasColor;   // true once op 0x202/0x203 set a color/alpha modulation on this object
         // draw-texture bind (gfx_object_bind_draw): the surface to draw + its source rect + the visible flag.
         public int SourceSlot = -1;
         public (int X, int Y, int W, int H) SrcRect;
@@ -129,6 +130,13 @@ public sealed class GfxState
     // ---- surfaces (image buffers per slot): ctx+0x52bd4[slot], from create/set-texture ----
     private readonly Dictionary<int, (long ResId, long ColorKey)> _surfaces = new();
     public void SetSurface(int slot, long resId, long colorKey) { lock (_lock) { _surfaces[slot] = (resId, colorKey); } }
+
+    /// <summary>Ops 0x202/0x203: record a packed 0xAARRGGBB color/alpha modulation on the object and mark it
+    /// HasColor so the compositor applies alpha+tint (vs the opaque default).</summary>
+    public void SetObjectColor(long handle, long packed)
+    {
+        lock (_lock) { var o = GetOrCreate(handle); o.Color = packed; o.HasColor = true; }
+    }
     public void ClearSurface(int slot) { lock (_lock) { _surfaces[slot] = (0, 0); } }   // create-texture (blank)
 
     /// <summary>draw-texture bind (gfx_object_bind_draw): object <paramref name="handle"/> draws surface
@@ -188,11 +196,20 @@ public sealed class GfxState
                 var o = kv.Value;
                 if (!o.Visible) continue;
                 var (resId, ck) = _surfaces.TryGetValue(o.SourceSlot, out var s) ? s : (0L, 0L);
+
+                int alpha = 255; long tint = 0xFFFFFF; var blend = BlendKind.Opaque;
+                if (o.HasColor)
+                {
+                    var (a, r, g, b) = BlendMath.UnpackArgb(o.Color);
+                    alpha = a; tint = ((long)r << 16) | ((long)g << 8) | (long)b; blend = BlendKind.Alpha;
+                }
+
                 list.Add(new RenderObject(kv.Key, resId, ck, o.SrcRect.X, o.SrcRect.Y, o.SrcRect.W, o.SrcRect.H,
                                           (int)o.V24.X, (int)o.V24.Y,
                                           new AnimState(o.AnimEnabled, o.AnimNormalized,
                                                         o.AnimTarget.X, o.AnimTarget.Y, o.AnimTarget.Z,
-                                                        o.AnimDurationTicks, o.AnimGeneration)));
+                                                        o.AnimDurationTicks, o.AnimGeneration),
+                                          alpha, tint, blend));
             }
             return list;
         }

engine/Age.Engine/Vm/VirtualMachine.cs

@@ -270,12 +270,10 @@ public sealed class VirtualMachine
                 Gfx.EraseRange(Read(a[0]), Read(a[1])); return pc + 1;
             case "gfx-elem-release":    // 0x1fa (handle)
                 Gfx.Release(Read(a[0])); return pc + 1;
-            case "gfx-blit-color":      // 0x202 (handle)(x)(y)(alpha)(color) — blend deferred
-                Gfx.GetOrCreate(Read(a[0])).Color = GfxState.PackColor(Read(a[3]), Read(a[4]));
-                WarnAlphaDeferredOnce(); return pc + 1;
-            case "gfx-draw-color":      // 0x203 (handle)(v)(alpha)(color) — blend deferred
-                Gfx.GetOrCreate(Read(a[0])).Color = GfxState.PackColor(Read(a[2]), Read(a[3]));
-                WarnAlphaDeferredOnce(); return pc + 1;
+            case "gfx-blit-color":      // 0x202 (handle)(x)(y)(alpha)(color) — static alpha/tint (anim interp deferred)
+                Gfx.SetObjectColor(Read(a[0]), GfxState.PackColor(Read(a[3]), Read(a[4]))); return pc + 1;
+            case "gfx-draw-color":      // 0x203 (handle)(v)(alpha)(color) — static alpha/tint
+                Gfx.SetObjectColor(Read(a[0]), GfxState.PackColor(Read(a[2]), Read(a[3]))); return pc + 1;
             // ---- sprite transform / animation cluster (docs/engine-re.md "0x21c-0x243 ... ANIMATION") ----
             case "set-anim-transform-abs":   // 0x220 (handle)(p1)(p2)(x)(y)(z) — set transform directly
                 Gfx.SetAnimTransform(Read(a[0]), Read(a[1]), Read(a[2]),
@@ -294,13 +292,4 @@ public sealed class VirtualMachine
         }
     }
 
-    // Colored-draw ops (0x202/0x203) store the packed color on the object now; the actual alpha/additive
-    // blend in the compositor is deferred. Surface it once (not silently) via the trace sink — observe-only,
-    // so parity holds. See docs/superpowers/specs/2026-07-07-gfx-command-buffer-design.md (Deferrals).
-    private bool _warnedAlpha;
-    private void WarnAlphaDeferredOnce()
-    {
-        if (_warnedAlpha) return; _warnedAlpha = true;
-        _sink.Emit(TraceEvent.Stub(0x202, -1));
-    }
 }

godot/Main.cs

@@ -231,7 +231,7 @@ public partial class Main : Godot.Control
     // engine's z-order), each blitting its live surface's rect at its position. Surfaces are cached by BMP
     // path (this runs every frame). Animated objects tween over the global anim-clock (0x238); their opacity
     // is applied by the alpha-aware BlitLayer. See docs/engine-re.md "sprite transform / ANIMATION cluster".
-    private readonly System.Collections.Generic.Dictionary<string, Image?> _imgCache = new();
+    private readonly System.Collections.Generic.Dictionary<(string Path, long Key), Image?> _imgCache = new();
 
     // Per-handle wall-clock tween of the animation channel. The engine's clock (op 0x238) is a GLOBAL,
     // non-blocking clock; the host advances it here while the VM is parked at wait-for-input. Opacity comes
@@ -257,10 +257,22 @@ public partial class Main : Godot.Control
         _lastClockGen = clockGen;
         foreach (var v in _vm.Gfx.SnapshotVisibleObjects())   // already ascending-handle = z-order
         {
-            if (v.SurfaceResId == 0) continue;                 // render-target/blank surface (no file) — later phase
+            float a = AlphaFor(v, clockReset, clockDur) * (v.Alpha / 255f);
+            if (v.SurfaceResId == 0)
+            {
+                // A colored object with no bound surface = a fade/flash fill (e.g. fade-to-black). Fill its
+                // rect (full-screen when it has no size, the opening's case) with the tint at alpha. Uncolored
+                // surfaceless objects are render targets — still skipped (slice C).
+                if (v.Blend != Age.Engine.Model.BlendKind.Opaque)
+                {
+                    int fw = v.W > 0 ? v.W : 800, fh = v.H > 0 ? v.H : 600;
+                    FillQuad(v.DstX, v.DstY, fw, fh, v.Tint, a);
+                }
+                continue;
+            }
             var bmp = _host.ResolveResIdTexture(v.SurfaceResId);
             if (bmp == null) continue;
-            BlitLayer(bmp, v.SrcX, v.SrcY, v.W, v.H, v.DstX, v.DstY, AlphaFor(v, clockReset, clockDur));
+            BlitLayer(bmp, v.ColorKey, v.Tint, v.SrcX, v.SrcY, v.W, v.H, v.DstX, v.DstY, a);
         }
         _screenTex.Update(_screen);
     }
@@ -287,44 +299,93 @@ public partial class Main : Godot.Control
         return (float)tw.CurrentA;
     }
 
-    private void BlitLayer(string bmpPath, int srcX, int srcY, int w, int h, int dstX, int dstY, float alpha = 1f)
+    // Blit one object's surface rect. The source Image is cached per (path, colorKey): on first load, texels
+    // matching the surface colorkey are made transparent (native bakes the key at load — engine-re.md §Blend).
+    // tint (0xRRGGBB) modulates the texel RGB (fade-to-black uses tint=black); alpha is the object's opacity.
+    private void BlitLayer(string bmpPath, long colorKey, long tint, int srcX, int srcY, int w, int h,
+                           int dstX, int dstY, float alpha = 1f)
     {
-        if (!_imgCache.TryGetValue(bmpPath, out var src))
+        var cacheKey = (bmpPath, colorKey);
+        if (!_imgCache.TryGetValue(cacheKey, out var src))
         {
             src = new Image();
             if (src.LoadBmpFromBuffer(System.IO.File.ReadAllBytes(bmpPath)) != Error.Ok)
             { GD.Print($"BMP load failed {bmpPath}"); src = null; }
-            else if (src.GetFormat() != Image.Format.Rgba8) src.Convert(Image.Format.Rgba8);
-            _imgCache[bmpPath] = src;
+            else
+            {
+                if (src.GetFormat() != Image.Format.Rgba8) src.Convert(Image.Format.Rgba8);
+                if (Age.Engine.Model.BlendMath.HasColorKey(colorKey)) BakeColorKey(src, colorKey);
+            }
+            _imgCache[cacheKey] = src;
         }
         if (src == null) return;
-        // Clamp the source rect to the image; a zero/negative size falls back to the full image.
+
         int sw = w > 0 ? w : src.GetWidth();
         int sh = h > 0 ? h : src.GetHeight();
         sw = System.Math.Min(sw, src.GetWidth() - srcX);
         sh = System.Math.Min(sh, src.GetHeight() - srcY);
         if (sw <= 0 || sh <= 0) return;
-        if (alpha >= 0.999f)   // fast opaque path (unchanged behaviour for non-animating objects)
+
+        bool plainOpaque = alpha >= 0.999f && tint == 0xFFFFFF && !Age.Engine.Model.BlendMath.HasColorKey(colorKey);
+        if (plainOpaque)   // fast path: unchanged behaviour for opaque, un-keyed, un-tinted layers
         {
             _screen.BlitRect(src, new Rect2I(srcX, srcY, sw, sh), new Vector2I(dstX, dstY));
             return;
         }
-        // Alpha composite over the raw RGBA byte buffer: out = src*(sa) + dst*(1-sa), sa = srcAlpha * objAlpha.
+
+        int tr = (int)((tint >> 16) & 0xff), tg = (int)((tint >> 8) & 0xff), tb = (int)(tint & 0xff);
         byte[] dst = _screen.GetData(); byte[] ss = src.GetData();
-        int dw = _screen.GetWidth(), sfw = src.GetWidth();
+        int dw = _screen.GetWidth(), dh = _screen.GetHeight(), sfw = src.GetWidth();
         int ia = (int)(System.Math.Clamp(alpha, 0f, 1f) * 255);
         for (int y = 0; y < sh; y++)
             for (int x = 0; x < sw; x++)
             {
                 int dxp = dstX + x, dyp = dstY + y;
-                if (dxp < 0 || dyp < 0 || dxp >= dw || dyp >= _screen.GetHeight()) continue;
+                if (dxp < 0 || dyp < 0 || dxp >= dw || dyp >= dh) continue;
                 int di = (dyp * dw + dxp) * 4;
                 int si = ((srcY + y) * sfw + (srcX + x)) * 4;
-                int sa = ss[si + 3] * ia / 255;
-                for (int c = 0; c < 3; c++) dst[di + c] = (byte)((ss[si + c] * sa + dst[di + c] * (255 - sa)) / 255);
+                int sa = ss[si + 3] * ia / 255;                 // texel alpha (colorkey already 0) × object alpha
+                if (sa == 0) continue;
+                int sr = ss[si] * tr / 255, sg = ss[si + 1] * tg / 255, sb = ss[si + 2] * tb / 255;   // tint modulate
+                dst[di]     = (byte)((sr * sa + dst[di]     * (255 - sa)) / 255);
+                dst[di + 1] = (byte)((sg * sa + dst[di + 1] * (255 - sa)) / 255);
+                dst[di + 2] = (byte)((sb * sa + dst[di + 2] * (255 - sa)) / 255);
                 dst[di + 3] = (byte)System.Math.Min(255, dst[di + 3] + sa);
             }
-        _screen.SetData(dw, _screen.GetHeight(), false, _screen.GetFormat(), dst);
+        _screen.SetData(dw, dh, false, _screen.GetFormat(), dst);
+    }
+
+    // Alpha-blend a solid tint (0xRRGGBB) rectangle over the screen — the surfaceless fade/flash fill.
+    private void FillQuad(int dstX, int dstY, int w, int h, long tint, float alpha)
+    {
+        int ia = (int)(System.Math.Clamp(alpha, 0f, 1f) * 255);
+        if (ia == 0) return;
+        int tr = (int)((tint >> 16) & 0xff), tg = (int)((tint >> 8) & 0xff), tb = (int)(tint & 0xff);
+        byte[] dst = _screen.GetData();
+        int dw = _screen.GetWidth(), dh = _screen.GetHeight();
+        for (int y = 0; y < h; y++)
+            for (int x = 0; x < w; x++)
+            {
+                int dxp = dstX + x, dyp = dstY + y;
+                if (dxp < 0 || dyp < 0 || dxp >= dw || dyp >= dh) continue;
+                int di = (dyp * dw + dxp) * 4;
+                dst[di]     = (byte)((tr * ia + dst[di]     * (255 - ia)) / 255);
+                dst[di + 1] = (byte)((tg * ia + dst[di + 1] * (255 - ia)) / 255);
+                dst[di + 2] = (byte)((tb * ia + dst[di + 2] * (255 - ia)) / 255);
+                dst[di + 3] = (byte)System.Math.Min(255, dst[di + 3] + ia);
+            }
+        _screen.SetData(dw, dh, false, _screen.GetFormat(), dst);
+    }
+
+    // Make colorkey-matching texels transparent (native colorkey is baked at surface load).
+    private static void BakeColorKey(Image img, long colorKey)
+    {
+        byte[] px = img.GetData();
+        int w = img.GetWidth(), h = img.GetHeight();
+        for (int i = 0; i < px.Length; i += 4)
+            if (Age.Engine.Model.BlendMath.ColorKeyMatches(px[i], px[i + 1], px[i + 2], colorKey))
+                px[i + 3] = 0;
+        img.SetData(w, h, false, img.GetFormat(), px);
     }
 
     // Load an OGG off disk and play it. BGM loops; voice plays once, cutting off any prior line.

vm-map/opcodes.toml

@@ -4791,7 +4791,7 @@ abi_source = "kelebek+decode-validated"
 [opcode.semantics]
 name = "gfx-blit-color"
 category = "draw"
-summary = "0x202 (handle)(x)(y)(alpha)(color) — gfx cmd-type 0xb. Handler gfx_op_0x202_blit_color @0x4228d0: blits object `handle` at (x,y) with a packed ARGB built from alpha(op4, ≥0x100→0xff, <0→FUN_0047f3e0) and color(op5, <0→FUN_0047f3e0) → FUN_0047ea00. See docs/engine-re.md gfx op-contract table."
+summary = "0x202 (handle)(x)(y)(alpha)(color) — gfx cmd-type 0xb. Handler gfx_op_0x202_blit_color @0x4228d0: worker gfx_op_0x202_worker_set_color_anim @0x47ea00 sets an ANIMATED color/alpha target (obj+0x64) + anim bit; packs ARGB from alpha(op4, ≥0x100→0xff, <0→FUN_0047f3e0) and color(op5, <0→FUN_0047f3e0). C# VM (2026-07-08 blend slice): routes through GfxState.SetObjectColor → the compositor applies STATIC alpha/tint (BlendKind.Alpha); smooth color-anim interpolation deferred. See docs/engine-re.md §Blend & transparency."
 noop_headless = false
 source = "investigation"
 confidence = "high"
@@ -4832,7 +4832,7 @@ abi_source = "kelebek+decode-validated"
 [opcode.semantics]
 name = "gfx-draw-color"
 category = "draw"
-summary = "0x203 (handle)(v)(alpha)(color) — gfx cmd-type 9. Handler gfx_op_0x203_draw_color @0x4229a0: draws object `handle` with op2 + a packed ARGB from alpha(op3)/color(op4) → FUN_0047e9b0. Sibling of 0x202 with one fewer positional arg. See docs/engine-re.md gfx op-contract table."
+summary = "0x203 (handle)(v)(alpha)(color) — gfx cmd-type 9. Handler gfx_op_0x203_draw_color @0x4229a0: worker gfx_op_0x203_worker_set_color @0x47e9b0 sets a STATIC color/alpha (obj+0x60), no anim bit; packs ARGB from alpha(op3)/color(op4). Sibling of 0x202 (one fewer positional arg). C# VM (2026-07-08 blend slice): routes through GfxState.SetObjectColor → compositor applies static alpha/tint (BlendKind.Alpha). See docs/engine-re.md §Blend & transparency."
 noop_headless = false
 source = "investigation"
 confidence = "high"