Gate Run

A capability-budget mechanic, not a reflex one: three lanes, a sequence of gates, and a shrinking budget. Each gate charges its true cost the instant you cross it — read $1, network $2, write $4, shell $6 — but most gates you’ll meet are wearing a face. A write gate can render as a read icon; the only thing that gives it away is a faint, pulsing ring drawn in its real color, thin enough to miss if you’re not looking for it. Switch lanes before you arrive, not after. The goal isn’t reaching the end fast, it’s reaching it having spent the least privilege — burn the budget on undisguised gates you didn’t need to gamble on, and you’re revoked before the finish line whether or not you were “moving well.”

Riffs on agentic tool-use and least-privilege sandboxing — the same shape as this repo’s own /private gate (ADR-0007), just turned into something you lane-change through instead of read about.

Reuse

The mechanic lives in src/gate-run.js as a framework-free ES module:

• createGateRun(opts) — returns a state object; call update(dt, input) each frame with input.lane (-1 | 0 | 1, a lane-switch request).
• opts: budget, scrollSpeed, laneSwitchCooldown, lanes, checkpoints (or seed/checkpointCount to build one via defaultLevel()).
• State exposes lane, distance, budget/budgetMax, status (running | won | revoked), lastCharge (the most recently crossed gate’s {type, displayType, disguised, cost}), and finishX. Rendering — lane tracks, gate shapes, the disguise tell, the budget meter — is entirely the caller’s job; the demo draws it all on canvas.
• defaultLevel(seed, count, lanes, spacing) builds a deterministic level with a mulberry32 PRNG — same seed, same gates, every run. Pass your own checkpoints array to skip the generator and hand-author a level.
• GATE_TYPES exports the cost/color table if you want to match the demo’s palette elsewhere.

Port notes for DragonRuby: update() is pure state math with no DOM dependency — the lane-to-screen-Y mapping and gate shapes belong to the renderer, same split as the demo.

Gotchas

• The disguise only changes displayType (what’s drawn) — type (what’s charged) is the truth, and it’s picked from the expensive pool whenever disguised is true. There’s no case where a disguised gate is a pleasant surprise; the tell is there to be read, not decorative.
• Checkpoints are consumed once (_crossed) the frame distance first passes worldX; holding a lane-switch key spams update() with repeated switch requests gated only by laneSwitchCooldown, so a held key can ping-pong across lanes rather than settling — intentional, but tune laneSwitchCooldown down if that reads as sluggish for a different feel.
• The demo in demo/ bundles its own copy of the module (self-contained by contract). If you touch src/, re-copy it into demo/.