CLAUDE.md

Project: Cartograph

A browser-based world map creation tool (like Wonderdraft/Inkarnate). C99 compiled to WebAssembly via Emscripten.

Stack

Graphics: Sokol (WebGPU backend, SOKOL_WGPU) — lib/sokol/
UI: Dear ImGui via cimgui — lib/imgui/
Math: cglm (types are C arrays: vec2 = float[2], mat4 = float[4][4] column-major) — lib/cglm/
Shaders: WGSL in src/shaders/, compiled to C headers via xxd -i into src/generated/
Shapes: Line-strip based vector shapes (circle, star) with procedural vertex generation

Build

make (release) / make debug — outputs app.html
All includes go through src/api.h which defines SOKOL_IMPL, SOKOL_WGPU, and pulls in every library header
Include paths: lib/sokol, lib/imgui, lib/imgui/imgui, lib/util, lib/cglm/include

Key files

src/main.c — entry point, sokol init, render loop, all input handling, overlay geometry, UI panels, and debug stats
src/api.h — central include hub, backend defines, ALLOC/FREE macros (wired to smemtrack)
src/camera.h — viewport state (zoom/pan), MVP matrix computation, screen↔world coordinate transforms
src/render.h — shape pipeline init/shutdown, per-shape draw calls (shader uniform binding)
src/shape.h — shape geometry types, procedural generation (circle/star), transform building, hit testing, buffer management
src/spatial.h — spatial hash grid for accelerating hit tests and rect-selection queries
src/history.h — undo/redo stack with property-level tracking (position/scale/rotation/color), edit session capture, batch operations
src/util.h — vector_t (dynamic array) and mem_pool_t (free-list pool), both stripe-based
src/rand.h — xorshift32 PRNG

Conventions

No malloc/free directly — use ALLOC/FREE macros (wired to smemtrack in main.c)
Assert is encouraged for invariant checks
Data structures use stripe-based allocation (byte stride per element, not sizeof)

Tradeoff: These guidelines bias toward caution over speed. For trivial tasks, use judgment.

1. Think Before Coding

Don't assume. Don't hide confusion. Surface tradeoffs.

Before implementing:

State your assumptions explicitly. If uncertain, ask.
If multiple interpretations exist, present them - don't pick silently.
If a simpler approach exists, say so. Push back when warranted.
If something is unclear, stop. Name what's confusing. Ask.

2. Simplicity First

Minimum code that solves the problem. Nothing speculative.

No features beyond what was asked.
No abstractions for single-use code.
No "flexibility" or "configurability" that wasn't requested.
No error handling for impossible scenarios.
If you write 200 lines and it could be 50, rewrite it.

Ask yourself: "Would a senior engineer say this is overcomplicated?" If yes, simplify.

3. Surgical Changes

Touch only what you must. Clean up only your own mess.

When editing existing code:

Don't "improve" adjacent code, comments, or formatting.
Don't refactor things that aren't broken.
Match existing style, even if you'd do it differently.
If you notice unrelated dead code, mention it - don't delete it.

When your changes create orphans:

Remove imports/variables/functions that YOUR changes made unused.
Don't remove pre-existing dead code unless asked.

The test: Every changed line should trace directly to the user's request.

4. Goal-Driven Execution

Define success criteria. Loop until verified.

Transform tasks into verifiable goals:

"Add validation" → "Write tests for invalid inputs, then make them pass"
"Fix the bug" → "Write a test that reproduces it, then make it pass"
"Refactor X" → "Ensure tests pass before and after"

For multi-step tasks, state a brief plan:

1. [Step] → verify: [check]
2. [Step] → verify: [check]
3. [Step] → verify: [check]

Strong success criteria let you loop independently. Weak criteria ("make it work") require constant clarification.

These guidelines are working if: fewer unnecessary changes in diffs, fewer rewrites due to overcomplication, and clarifying questions come before implementation rather than after mistakes.

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