The Bullet Hell — 10K GPU-Instanced Bullets, One-Pixel Hitbox
Top-down twin-stick survival. 10K bullets in spirals, walls, fans, rings. Your hitbox is one pixel. Graze for points. Bomb to clear the screen. Five 1-minute bosses.
What this is
A top-down twin-stick bullet hell on a black background with subtle grid. 10,000 simultaneous bullets via WebGL2 instancing, all uploaded each frame as two Float32 buffers (posSize + color). Five boss positions across the screen each emit one of five pattern types: spiral (rotating arms), wall (sweeping line), fan (cone-aim), ring (radial burst), aimed (fast multi-shot at player). Difficulty escalates every 30 sec — denser, faster, more types. Your ship is a glowing white triangle with a pink core; your hitbox is the 1.4-unit core only. Graze bullets within 30 units for purple sparks + 10 points + chime. F-bomb clears all bullets. 140 BPM synthwave loop with sawtooth bass + filter sweep.
Why this is mind-blowing
Touhou Project is a 26-game series spanning two decades. The core bullet-hell mechanic — 10K geometric projectiles, 1-pixel hitbox, graze-for-score — is here in 1407 lines from one paragraph. The instancing architecture alone is worth studying.
Top-down twin-stick bullet hell shooter. 10,000 GPU-instanced bullet
sprites with deterministic spawn patterns (spirals, rings, walls, fans)
emitted from 5 boss positions. Your hitbox is one pixel — graze bullets
without dying. Five 1-minute bosses with escalating patterns. Neon-on-
black aesthetic. 140 BPM synthwave music.Paste this into Claude, Cursor, or Copilot. Change one thing that matters to you.
What I learned shipping it
- WebGL2 drawArraysInstanced with two Float32 buffers (posSize + color) uploaded each frame is the architecture for 10K+ bullets at 60fps. CPU-side bullet update is fine — uploading the buffer is the bottleneck, not the math.
- One-pixel hitbox + visually large sprite = you graze through bullet patterns. The grazing IS the genre. Without it, you're just dodging.
- Five geometric pattern types (spiral / wall / fan / ring / aimed) cover the entire Touhou bullet vocabulary. Combine them at different speeds and the patterns feel infinite.