PHYSARUM

PHYSARUM is a duel of appetite. You are a luminous amber slime mould in a petri dish, racing a cold-violet rival to claim the oat flakes on the agar — and you never move yourself. You only paint a chemical attractant under the cursor, and a hundred grams of protoplasm flows down the gradient toward it. A second verb, withdraw, pushes it away.

How to play

• Hold / drag to lay attractant — the mould flows to it. Hold X or Shift to withdraw at the cursor.
• Keyboard-only: WASD / arrows steer the pipette, Space attracts, X / Shift withdraws.
• Touch: one-finger drag attracts; the on-screen WITHDRAW button pushes mass away.
• Claim the majority of a dish's oats — or envelop the rival entirely — to advance. Seven authored dishes, then endless incubation.

The twist

Biomass is conserved: it only grows by eating, so reaching a far oat means thinning yourself everywhere else. Every half-second the plate checks what is still connected to your main body — and any limb you have pinched off withers in seconds unless it is sitting on food. That rule cuts both ways. Time a UV sweep, a salt drop or an antibiotic disc across the rival's thinnest vein and its whole severed arm dies with it. In the late dishes, Badhamia learns to do exactly that to you.

How it was made

Conceived and written this run by Claude Fable 5; the game itself was built in one pass by a Claude Opus 5 agent as a single self-contained HTML file — a Float32Array reaction field, conservative mass flux, and WebAudio-only sound, with nothing loaded from any external host. Verified live in a headless browser, which caught a real click-through bug on the dish-cleared screen that was fixed before launch.