Order your bullets by name
Patterns are the vocabulary of the genre, and you can request them like toppings:
- Aimed shots — fired straight at you; teaches constant movement.
- Rings — expanding circles with gaps; teaches positioning.
- Spirals — rotating streams; teaches rhythm and patience.
- Fans — cone bursts that sweep; teaches reading ahead.
- Walls with gaps — the classic "find the door" moment.
A boss that cycles aimed → ring → spiral, faster each loop, is a complete fight — and one sentence on Arcade Sandbox.
The fairness kit (ask for all four)
The difference between "hard but I'll retry forever" and "closed the tab" is four cheats every great shmup uses:
- A tiny hitbox — the real collision zone is a few pixels at the ship's core, far smaller than the sprite. This is the genre's biggest open secret.
- Guaranteed paths — "every pattern must leave at least one navigable route."
- Telegraphs — a flash or windup before every big attack.
- Bombs — two or three per run that clear the screen. Panic insurance.
Prompt recipes
"A vertical bullet hell where I pilot a hummingbird defending a garden from clockwork wasps. Enemies fire rings and aimed shots; the wasp queen boss cycles spiral, fan, and wall patterns with telegraphed windups. Tiny hitbox shown as a glowing dot, graze points for near misses, 3 screen-clearing nectar bombs. Every pattern leaves a path."
"A horizontal shmup: a fax machine that gained sentience blasts through an endless 1990s office. Enemies are staplers, monitors, and manager drones firing memo-fans. Power-ups upgrade my paper stream from single to triple to laser. Boss every 90 seconds, each with two phases."
"A one-boss bullet hell duel, Undertale-energy: just me and an opera-singing moon whose attacks follow her aria — bullets pulse on the beat description. Five verses, five patterns, dramatic finale. Tiny hitbox, instant retry from the verse I died on."
▶ FIRST GAME'S FREE
New accounts start with ⚡ 5 free tokens — a 2D build costs 4. Describe the chaos; the AI does the math.
Build my shmup →Difficulty tuning is a 3-token revision: "20% fewer bullets, 10% slower."
Graze scoring: the genre's secret sauce
Reward players for almost dying: points for bullets that pass within a whisker. Graze scoring turns dodging from survival into style, and creates the risk-reward loop that makes score chasers replay for weeks. One line: "award graze points when bullets pass close without hitting, with a satisfying tick sound description and a combo multiplier."
Tune with intent
- Overwhelmed instantly? "Slow all bullets 15% and thin the first minute's density by a third."
- Too easy? "Add a second simultaneous pattern after wave 5."
- Deaths feel cheap? "Shrink the hitbox further and add a brief invulnerability flash after each hit."
FAQ
Vertical or horizontal?
Vertical (bullets fall toward you) reads better on phones; horizontal feels more like a journey. Say which — or ask for the screen to fit both orientations.
Can it handle hundreds of bullets in a browser?
Canvas-based 2D games handle bullet-hell densities comfortably on modern devices. If a build chugs on an old phone, "cap simultaneous bullets at 200" is a one-line revision.
Twin-stick or fixed shooting?
Classic shmups auto-fire forward while you dodge. If you want to aim independently of movement, you're describing a top-down twin-stick shooter — that's its own guide.
What does it cost?
First 2D game effectively free (5 welcome tokens; builds cost 4), then ~$4 per game, 3 tokens per tuning pass.