Pulsar

A TypeScript reimagining of the 1979 Atari classic, focused on rhythm. You are in the da

Stack

• TypeScript
• Vite (dev server + build)
• HTML5 Canvas 2D with additive blending for the glow

No game libraries — the engine is hand-rolled in src/.

Run it

npm install
npm run dev

Then open the URL Vite prints.

Dev pages

Alongside the game itself, the dev server serves a few authoring/inspection pages:

Path	What it's for
/sprites	Every drawable body in the game on one contact sheet, rendered live — zoom, tumble, collision-surface overlay, and a reroll to resample the seeded silhouettes. Loads no audio code at all, so it never starts a sound bake.
/sound	Sound editor — tunes public/sounds/config.json.
/music	Music editor.
/piano-roll	Piano-roll view of the score.

Controls

Key	Action
← / → (or A / D)	Rotate
↑ (or W)	Thrust
space	Fire
H	Hyperspace (teleport, 2.5s cooldown)
esc	Pause / resume
M	Mute / unmute
enter	Begin / restart

Rhythm

The whole game runs against a shared beat clock on a 0.5-second grid (120 BPM quarters). Two things happen on that clock:

• Bassteroids play the song. Four armoured bassteroid kinds (bassA, bassB, bassC, bassD) sit on the four beats of a 4-beat measure — A on beat 1, B on beat 2, C on beat 3, D on beat 4. Each kind has its own percussive voice tuned to a different note in C major: A is the kick (C2 root), B the pluck (G2 fifth), C the boom (F2 fourth), D the snap (C3-area accent). With all four on the field the pattern reads as a clean kick-pluck-boom-snap, and any subset of them still harmonises. A large bassteroid has 4 HP and takes that many shots before exploding, each hit leaving a visible crack across the hull. The final hit splits it into two medium pieces (2 HP each); medium splits again into two small pieces (1 HP, terminal). Children inherit the parent's kind (so the parent's voice) but their beat slots subdivide the measure — gen-1 pieces sit half a measure apart, gen-2 pieces a quarter measure apart, so by the time a large is fully broken down its four small pieces carry that kind's voice onto every beat. Decorator asteroids — chime, bell, warble, and the rare tink crystal — sit on top with their own melodic timbres so each wave's soundscape is unique.
• Your shots count toward combo. Any shot fired (or any kill that lands) within ±150 ms of a beat center is an "on-beat" event. Consecutive on-beat events build a combo, scaling the score multiplier up to ×5. Miss a beat window and the combo resets. The ship's silhouette pulses exactly in the same window — that glow flare is a literal preview of the rhythm gate.

The combo readout pops up on the HUD once you reach ×2, and a small gold sparkle ring fires off any on-beat kill so the bonus reads visually even when the underlying asteroid hue is similar to the explosion.

Waves

Wave 1 starts at 4 plain asteroids. The total count grows by one every other wave. Bassteroids are seeded with a deliberate "learn one before you learn two" intro: a single random bassteroid kind appears in wave 2, a different random kind in wave 3, and both of those appear together in wave 4. From wave 6 onward the every-other-wave unlock cadence resumes, adding chime, bell, warble, then the two remaining bassteroid kinds. From wave 3 onward there's also a 1-in-3 chance per wave that a single small tink crystal will appear as a bonus. The result is that the audio bed layers up smoothly as you climb: a quiet field at wave 1, a full ensemble by the time you're 10 waves in.

Powerup canisters

Roughly one in three waves a glowing canister drifts in somewhere mid-level (8–24s into the wave). Only one can appear per wave, the timing is randomised, and the kind is rolled fresh. Fly over it to absorb — read the letter on the capsule to know what you grabbed:

Letter	Powerup	Effect
T	Trident	Fires a 3-bullet spread until you die
R	Rapid Pulse	Fires every 8th note (2× cadence) until you die, and 8th beats count for combo while it's active
P	Piercing Plasma	Bullets punch through asteroids until you die
S	Shield Bloom	Absorbs one collision, then pops
Z	Slow Tide	The whole music side of the clock (beat, bassteroids, asteroid motion) crawls at ~half speed for 8s while you and your bullets keep full speed — it's bullet-time, not pause

Sound

All sound is procedurally synthesized at runtime via the Web Audio API — no asset files.

• Fire is a downward-glide triangle with a high shimmer overlay.
• Explosions are filtered noise bursts plus a sub-sine sweep, scaled by asteroid size.
• Thrust is a band-passed noise loop with a saw-rumble, gated by the thrust key.
• Hyperspace is a glissando sine plus rising bandpass noise.
• Wave-clear is a four-note ascending chord.
• Bass kick / pluck / boom / snap are the four percussive voices of the bass kit: C2 sine-thump (bassA), G2 saw+triangle plucked-bass (bassB), F2 sine-with-sub punch (bassC), and a snare-leaning noise+C3-triangle accent (bassD). The notes form a I-IV-V triad with a percussive accent, so any combination of the four layered on a beat stays in key.
• Bass hit is a deep gravelly crunch — sub-bass sawtooth pair sweeping into the bass floor with a low-passed noise transient — that announces every bassteroid hit (a "you cracked the armour" cue, played on damage hits as well as the killing hit).
• Chime / bell / warble / tink are the decorator hit sounds — wind-chime partials, inharmonic temple bell, vibrato'd vocal "ooo", and a high glassy fifth respectively.
• Combo tick is a tiny high-passed noise click confirming an on-beat shot; combo sparkle is a warm mid-range fifth that rings out on an on-beat kill.
• Powerup is an ascending C-major arpeggio with a sparkle overlay; shield pop is a glassy ting with a noise wash.

Everything is routed through a soft compressor so layered hits don't clip.

Design notes

A few principles the code keeps coming back to:

• The wave is the music. Every special asteroid kind is first a sound and second a sprite — the audio bed is the reward for surviving long enough to unlock it. New types unlock by adding a layer, not replacing one.
• No assets, ever. Every pixel and every sample is generated at runtime: asteroid silhouettes from summed cosine harmonics, particle glow from cached radial gradients, music from raw OscillatorNodes. The repo has no assets/ folder and there is no plan to add one.
• Feel is tuned in comments, not docs. The beat window is ±150 ms because the dt cap is 50 ms plus normal human slop, but narrow enough that spam-firing only catches ~half of beats. The tink crystal is rare on purpose ("if you start seeing tink asteroids every wave, lower the per-wave spawn chance"). Slow-mo slows the music side of the clock (beat, bassteroids, asteroid motion) while leaving the ship and its bullets at full speed, so it reads as "bullet-time advantage" rather than a global pause. These tradeoffs live next to the constants that encode them.
• Bioluminescent palette, organic shapes. HSL hue rotation, additive blending, soft halos, and Fourier-sampled outlines instead of the classic Atari polygon. The asteroid field reads more like jellyfish drifting than rocks tumbling. The bassteroids are the deliberate exception — hard-edged modular silhouettes (hauler, tri-cluster, cross-station, tower) so the "play the rhythm" pieces look like built objects against the organic field.
• Aggressive sprite caching. glow.ts caches per-hue radial gradients in 15° buckets, asteroids pre-render their static body to an offscreen canvas at construction time, and the nebula bakes once and translates per frame. The single biggest Canvas2D perf lever in the codebase is "don't allocate a gradient inside a render loop."
• Small, named vocabularies. Five powerups, nine asteroid kinds, one hue palette — kept short on purpose so each member stays recognizable instead of disappearing into a long list.

Files

• src/Game.ts — main state machine, waves, collisions, beat clock, HUD wiring
• src/Ship.ts — player physics + glowing-triangle rendering with thrust plume and beat-pulse halo
• src/Asteroid.ts — organic outline, drifting nuclei, filament weave, bass-tempo bookkeeping, modular bassteroid sprites + HP/crack-damage rendering
• src/Shard.ts — Voronoi-style fragmentation when an asteroid dies
• src/Bullet.ts — plasma droplets with trail; carries the on-beat flag from the firing frame
• src/Canister.ts — drifting powerup canisters + pickup helpers
• src/Particle.ts — additive glow particles
• src/Starfield.ts — parallax stars + pre-rendered drifting nebulae
• src/Sound.ts — Web Audio synthesis (fire / explosion / thrust / death / hyperspace / wave-clear / bass / decorator / combo / powerup / shield)
• src/Input.ts — keyboard polling
• src/glow.ts — per-hue radial-gradient sprite cache used by particles, bullets, and canisters
• src/vec.ts — vector math + random helpers

Deploy

This is a static Vite app, so it deploys to Vercel as-is — Vercel auto-detects the Vite framework, runs npm run build, and serves dist/. No vercel.json is required.

To deploy manually:

npx vercel       # first time, links the project
npx vercel --prod

Or push to a GitHub repo connected to Vercel and every push to main will redeploy.

License

MIT