Creature Lab

Draw a creature. Evolve a brain. Watch it learn to walk.

Creature Lab is an evolution sandbox. You build a 2D creature out of limbs and motorised joints. Then a neural network learns to drive those joints. Nobody programs it: brains are bred, mutated and scored over hundreds of generations, until a twitching heap gets up and walks.

Same body, same ground, same 12 seconds: generation 1 (the ghost) against generation 194.

How it works

1. Build

Drag out limbs, drop in hinges and welds, and set each joint's range and strength. Tune a limb's thickness, density and friction. Give it eyes if you want it to see the ground ahead. Or start from a preset: biped, quadruped, spider, cheetah, crab, hopper, worm or ornithopter.

2. Evolve

A population of 100 creatures, each with a random brain, gets 12 seconds to go as far as it can. The best breed, their children mutate, and it repeats. Every core in your machine runs trials in parallel, and Turbo mode stops drawing so all of them go to evolution.

3. Watch and dig in

Replay any creature from any generation, exactly as it ran. Line up a generation in the arena, race a creature against the all-time best as a ghost, or scrub the fitness chart to see where it figured something out.

Every body plan finds its own gait. The ornithopter learned to fly 42 m.

What's inside

• Real physics. Rapier 2D (WebAssembly) or Planck.js (Box2D). Mass, torque, friction and falls all count.
• Real brains. Feed-forward or recurrent networks, or central pattern generators. Inputs are joint angles, ground contact, tilt, velocity, eyes and an evolved clock.
• Several ways to learn. A genetic algorithm, an evolution strategy (sep-CMA-ES), gradient training (PPO), or breeding plus polishing. Lifetime learning lets weights change within a single run.
• Fitness you design. Reward distance, height or flight. Penalise falls, flips, slipping or wasted energy. Race on flat ground, hills, rough terrain, stairs or gaps.
• Deterministic. Same creature, seed and settings, same run. Every replay is exact.
• Yours. Labs save automatically, run offline and export to a file. No account.
• Community gallery (opt-in). Share a creature, with its evolved brain if you want, or adopt someone else's and evolve it further.

Free demo vs. full edition

The demo runs right on this page, and on creaturelab.app. It's the whole app with a few locks:

	Demo (free)	Full edition
Presets	Biped, quadruped	All eight, including spider, cheetah, crab and ornithopter
Creature editor	Yes	Yes
Generations	Unlimited	Unlimited
Labs kept at once	1	Unlimited
Save creatures, import and export	No	Yes
Generation browser: replay, compare, arena	No	Yes
Evolution strategy, PPO training, Rapier engine	No	Yes
Share to the community gallery	Browse and adopt	Browse, adopt and share
Windows desktop app	No	Yes

What you get when you buy

• The Windows desktop app. It updates itself, and every update is signed and verified before it installs. It isn't code-signed yet, so the first time you run it, Windows SmartScreen will warn you: click More info, then Run anyway.
• The full edition in any browser, on any computer. Your itch.io download key unlocks it. Open your download page and copy the last part of its address, after /download/. Then in Creature Lab, click the version number beside the logo and paste it into the Key box. Your key works on several devices.
• Every future update, at no extra cost.

Mac: no native Mac build here yet. Your key unlocks the full edition in your Mac's browser.

System requirements

• Any recent Chrome, Edge, Firefox or Safari. Desktop recommended; it works on phones and tablets, but it's cramped.
• Evolution uses every CPU core you have. More cores means more generations per minute. You can dial it back under Settings, Power use.
• Windows app: Windows 10 or 11, 64-bit.

Privacy

Everything runs on your machine. Nothing you build or type leaves it unless you press Share, and the gallery can be switched off in Settings. The web version counts anonymous usage, like which features get used, and respects Do Not Track. The desktop app sends no analytics.