Tier A: SPRITECOLLIDE, runtime hints, tutorial runOnEdit

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ### Unreleased
 
+- **Runtime hints**: **`goto` / `gosub` / `on` / `if … then`**, **`DIM` / `FOR` / `NEXT`**, and **array subscripts** — short **`Hint:`** lines for common mistakes (missing line/label, **`THEN`**, bounds, parentheses, reserved names). **Native** `runtime_error_hint` prints **`Hint:`** on stderr (parity with WASM). **`tutorial-embed.js`**: **Ctrl+Enter** / **Cmd+Enter** runs; **`scrollToError`** (default **on**). **`web/tutorial.html`** playground mentions keyboard run.
+
+- **Sprites**: **`SPRITECOLLIDE(a, b)`** — returns **1** if two loaded, visible sprites’ axis-aligned bounding boxes overlap (basic-gfx + canvas WASM; **0** otherwise). Terminal **`./basic`** errors if used (requires **basic-gfx** or canvas WASM). **Runtime errors**: optional **`Hint:`** line for **unknown function** (shows name) and **`ensure_num` / `ensure_str`** type mismatches. **`tutorial-embed.js`**: optional **`runOnEdit`** / **`runOnEditMs`** for debounced auto-run after editing; **`web/tutorial.html`** enables this on the final playground embed only (**550** ms).
+
 - **Documentation**: **`docs/basic-to-c-transpiler-plan.md`** — design notes for a future **BASIC → C** backend (**cc65** / **z88dk**), recommended subset, and **explicit exclusions** (host I/O, `EVAL`, graphics, etc.).
 
 - **IF conditions with parentheses**: **`IF (J=F OR A$=" ") AND SF=0 THEN`** failed with **Missing THEN** because **`eval_simple_condition`** used **`eval_expr`** inside **`(`**, which does not parse relational **`=`**. Leading **`(`** now distinguishes **`(expr) relop rhs`** (e.g. **`(1+1)=2`**) from boolean groups **`(… OR …)`** via **`eval_condition`**. Regression: **`tests/if_paren_condition_test.bas`**.
@@ -70,7 +74,7 @@
 - **basic-gfx — hires bitmap (Phase 3)**
   - `SCREEN 0` / `SCREEN 1` (text vs 320×200 monochrome); `PSET` / `PRESET` / `LINE x1,y1 TO x2,y2`; bitmap RAM at `GFX_BITMAP_BASE` (0x2000).
 - **basic-gfx — PNG sprites**
-  - `LOADSPRITE`, `UNLOADSPRITE`, `DRAWSPRITE` (persistent per-slot pose, z-order, optional source rect), `SPRITEVISIBLE`, `SPRITEW()` / `SPRITEH()`; alpha blending over PETSCII/bitmap; `gfx_set_sprite_base_dir` from program path.
+  - `LOADSPRITE`, `UNLOADSPRITE`, `DRAWSPRITE` (persistent per-slot pose, z-order, optional source rect), `SPRITEVISIBLE`, `SPRITEW()` / `SPRITEH()`, `SPRITECOLLIDE(a,b)`; alpha blending over PETSCII/bitmap; `gfx_set_sprite_base_dir` from program path.
   - Examples: `examples/gfx_sprite_hud_demo.bas`, `examples/gfx_game_shell.bas` (+ `player.png`, `enemy.png`, `hud_panel.png`).
 
 ### 1.5.0 – 2026-03-20

README.md

@@ -379,6 +379,7 @@ Releases include **basic-gfx** — a full graphical version of the interpreter b
 - `DRAWSPRITE slot, x, y [, z [, sx, sy [, sw, sh ]]]` sets the **persistent** pose for that slot: the same image is drawn **every frame** until you call `DRAWSPRITE` again for that slot or the program exits (textures are freed when the window closes). **`x`, `y`** are **pixel** coordinates on the 320×200 framebuffer (not character rows): row *r* starts at **`y = r × 8`**. **`z`**: larger values paint **on top** (e.g. text/bitmap at 0, HUD at 200). Omit **`sx, sy`** to use the top-left of the image; omit **`sw, sh`** (or use ≤0) to use the rest of the texture from `(sx,sy)`. **Alpha** in the PNG is respected (transparency over text or bitmap).
 - `SPRITEVISIBLE slot, 0|1` hides or shows a loaded sprite without unloading.
 - `SPRITEW(slot)` / `SPRITEH(slot)` return pixel width/height after load (0 if not loaded yet).
+- `SPRITECOLLIDE(a, b)` returns **1** if the axis-aligned bounding boxes of two visible, drawn sprites overlap, else **0** (empty slots or hidden sprites never collide).
 - Example: `./basic-gfx -petscii examples/gfx_sprite_hud_demo.bas`
 - **Game shell** (`examples/gfx_game_shell.bas`): tile map from `DATA` with `POKE` (walls/floor/goal), **8×8 PNG** player (`player.png`) and enemy (`enemy.png`) via `DRAWSPRITE`, `INKEY$()` loop, HUD strip (`hud_panel.png`). Run: `./basic-gfx examples/gfx_game_shell.bas`