Add shapes and basic selective actions

CLAUDE.md

@@ -1,5 +1,34 @@
 # 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/`
+
+### 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, input (zoom/pan/drag)
+- `src/api.h` — central include hub, backend defines
+- `src/sprite.h` — sprite batching, texture manager, file import stubs
+- `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