A page section your visitors will remember.

A starting engine for round-based survival games, sampled as Brindlefen Holdout, an original night in a lamphouse on a fen. Foes rise from the reeds, walk a distance field to a window, tear its planks off one by one and climb through; you hold them off and hammer the boards back for points. Rounds grow in count, speed and health from a few numbers, every fifth one is a swarm, and four foe behaviours cover the genre: a walker, a sprinter, a brute that smashes two planks a blow and crashes through, and a lobber that arcs soot over the wall and must be shot through a window. Between rounds a vending terminal sells upgrades from a table of prices and effects.

The co-op partner is an AI ally on the same body as the player. Ten times a second it picks a task (revive you, board up the emptiest window, guard the window under most pressure), scores seventeen moves against the foes inside, soot about to land and your space, turns its aim at a set rate and calls out breaches, new threats and reloads. The simulation is a DOM-free fixed-step module, so a seeded run replays exactly and the same brain plays the attract mode. A high angled camera reads on phones and desktops; keyboard and mouse, or a touch stick with auto-aim. Rounds, foes, wares and the ally's lines are data tables in one config file.

How your agent works through it.

1. 01
   Name the world

   Write the setting, foe names, the terminal and the ally's lines into config.js. Keep the four behaviours; rename and redraw them for the new world in models.js.

2. 02
   Lay out the outpost

   Set the room size, windows, props and lamps. Every window needs a clear approach outside and a clear spot inside; the grid and fields are rebuilt from the table.

3. 03
   Tune rounds and the economy

   Shape the round curve and the wares' prices. Run the headless pilot for ten minutes on a few seeds and read rounds reached, downs and points before touching feel.

4. 04
   Tune the ally

   Adjust keep-away distance, aim turn rate, tolerance and callout gap until the ally helps without carrying the game. Watch it revive you under pressure.

5. 05
   Pick the opening and verify

   Script the attract opening (a breach in view), set the poster time, then test keys, mouse, touch stick, pause, reduced motion, 390 px and 1440 px, and a clean console.

Deliverables, not just a conversation.

Your agent will ask for

• The game's world and name: setting, the place being held, palette and tone
• The roster: which of the four foe behaviours to keep, their names, looks and numbers
• The round curve: foes per round, how many at once, speed and health growth, special rounds
• The economy: points per hit, kill and plank, and the terminal's wares, prices and effects
• The ally: name, how close it fights, how fast it aims, and the lines it calls out
• Target devices and inputs, and where it runs: campaign page, jam entry or team prototype

Runtime & requirements

• A browser with WebGL, Pointer Events and ES modules
• three.js 0.186.1 served locally through the import map
• Optional: Node.js 22+ to run the simulation and pilot headless
• Optional: Node.js 22+ and Playwright for poster export

The sample uses a fictional brief. Brand names, copy and figures in the demo are placeholders your agent replaces with yours; the skill tells it never to invent claims or numbers.

Choose your agent.

Preserve the complete folder. Check runtime dependencies and review scripts before execution.