Astrosaurus — an 8-bit dino astronaut platformer you play in the browser

Astrosaurus is a free retro platformer about a pixel-art T-rex in a space helmet. You hop across a 10,500-pixel asteroid field while your oxygen tank empties — and the emptier it gets, the heavier gravity pulls and the shorter your jumps become. One run is a race against your own decay toward the spacecraft at the far end.

It runs entirely in your browser. No download, no install, no account — press a key and go.

How to play

← → or A D — run left and right
Space or W — jump
Esc — pause
F — fullscreen
M — mute or unmute the music

Reach the spacecraft at the end of the level to win. Falling into the void, taking a single hit from debris, or running your oxygen to zero all end the run instantly.

The oxygen mechanic

Oxygen is the timer, the health bar and the difficulty curve all at once. It drains at two units per second and drags your physics down with it:

100% oxygen — normal gravity, full jump height
50% oxygen — gravity ×1.25, jumps ×0.85: gaps you cleared earlier start to bite
0% oxygen — gravity ×1.5, jumps ×0.7, and the run is over

There are only three cyan recharge stations in the whole level, at +30 oxygen each, and the gaps between them widen: 2,000 pixels to the first, 2,800 to the second, 3,500 to the third. The longest stretch is the one you enter with the weakest physics — that is the game.

Game features

Dynamic oxygen-driven physics — gravity and jump strength degrade as your tank empties
Three asteroid types: stable, crumbling on a 2-second timer, and vertically drifting
60+ asteroids across four escalating sections with three oxygen recharge stations
16 comet hazards streaking at angles plus 7 horizontal debris movers — one hit ends the run
Oxygen tanks scattered through the level for score
A run-end recap: how far you got, what killed you, and how close the next station was
Best-distance tracking saved in your browser
8-bit pixel art, chiptune audio, Phaser 3, 60 FPS, keyboard-only, no install

Tips for a first clear

Do not sprint the opening. Section one is the cheapest oxygen you will ever spend.
Crumbling asteroids give you two seconds — plan the next jump before you land, not after.
Debris kills on contact, so wait a beat rather than jumping into a comet's path.
Never skip a recharge station. The next stretch is always longer than the last.
Low on oxygen? Aim higher and earlier than feels right — your jump arc has already shrunk.

Frequently asked questions

Is Astrosaurus free to play?

Yes. Astrosaurus runs entirely in your browser and is free to play. There is no download, no install and no sign-up — open the page and the game loads.

What are the controls?

Move with the Arrow Keys or A and D. Jump with Space or W. Pause with Escape, toggle fullscreen with F and mute the music with M.

Why do my jumps get weaker as I play?

That is the core mechanic. Oxygen drains at 2 units per second and your physics degrade with it: at full oxygen you have normal gravity and jump height, at 50% gravity is 1.25× and jumps are 0.85×, and near empty gravity is 1.5× and jumps only 0.7×. Refill at one of the three cyan oxygen stations to reset your handling.

How long does one run take?

A full clear takes roughly two to two and a half minutes. The level is 10,500 pixels wide with more than 60 asteroids and four sections that get progressively longer and harder.

Can I play Astrosaurus on a phone or tablet?

Not yet. Astrosaurus is keyboard-only and needs a window of at least 1100 × 620 pixels, so it is a desktop and laptop game for now.

What is Astrosaurus built with?

It is a client-side HTML5 game built with Phaser 3 and Vite, rendered on a canvas with pixel-perfect 8-bit art at 60 FPS. There is no backend — progress and settings are stored in your browser.