Thunderfall: 10 minutes of vertical arcade bullet hell in the browser
The vertical shooter genre (or "danmaku") is unforgiving in the middle: too few bullets is boring, too many is unplayable. Thunderfall finds the balance: five sectors, at least 120 seconds each, and a boss you cannot cheese with a single bomb.
What the game is
You pick one of three ships and fly it up through enemy waves. Firing is automatic — all attention goes to the screen. The Falcon is fast and versatile, the Prism hits harder with thinner armour, and the Bastion survives where others explode.
Weapon drops come in four colours: blue fires a spreading fan, green pierces through everything, purple homes onto targets, and gold bursts over an area. Each weapon has its own level up to five, and switching weapons never loses a level.
Why it works
The bright dot at the ship's centre is the only hitbox. It is the genre's classic trick: the silhouette is wider than the hitbox, so slipping "through" a bullet counts as a graze and earns points plus thunder-drive charge. The eight-second drive boosts fire and clears the screen on start — but fresh bullet patterns still demand dodging.
Bosses are not health piñatas. Each one has three phases with barriers at 65% and 30% health: no single burst can skip a phase, and you survive the fire-pattern changes. Lasers draw a warning line before they fire — fair, but the room to move stays narrow.
Technology
A fully original work: plain JavaScript, screen 2D, real sound. No external assets, images or third-party libraries — art is procedurally drawn and audio is synthesized at runtime. The ships are procedural 3D meshes projected onto the 2D screen, banking on turns with engine glow.
The game was created with GPT-6 Astra by jackroc and released under CC0.