How Vault Raid AI actually investigates noise
A short deep-dive on Vault Raid stealth — how the noise meter, vision cones and guard chase logic interact, and why standing still beats sprinting.
Vault Raid is the only pure stealth title in the Skywar arcade. It uses three coupled systems — a noise meter, six guard vision cones, and a chase state machine — to create the feel of a small heist. This post walks through how those three systems interact.
The noise meter
Noise is a single floating-point value bounded between 0 and 2. It decays at -0.8 per second when you stop moving. Sprinting adds +3.8 per second; cracking a vault adds +1.6 per second; a decoy throw adds a flat +1.1 instantly. The math is exposed for a reason: it lets us tune behaviors discretely without tuning a thousand thresholds.
Vision cones
Each guard renders a visible cone on the floor — that cone is its detection cone. Step inside, within roughly 90 pixels of the guard, and you are spotted. Outside the cone, guards do not see you visually. The cones are not just visual decoration: they encode line-of-sight, length, and rotation as the guard turns.
How the two systems combine
Detection works in three layers, and they are evaluated separately each tick:
- If you are inside a guard's cone and within ~90px, you are spotted. Vision check first.
- Otherwise, if noise is above 1.1 and you are within 330px of a guard, the guard "hears" you and pivots to investigate. This works through walls.
- Otherwise, if noise is above 0.6 and you are within 450px, the guard becomes suspicious — they walk toward your last known position, but do not start a chase.
Why standing still works
Because noise decays at -0.8/sec when you are not moving, standing still after a vault crack is the fastest way to reset the chase. Two seconds of stillness after a full vault crack drops noise from 2 to roughly 0.4 — below the hearing threshold. The math is the whole reason "hold still, count to three, move" works as a strategy.
Why decoys are situational
A decoy throw spikes your own noise by 1.1 instantly. If you throw a decoy while already at 1.0 noise, you are now at 2.1 — over the cap, so it clips to 2.0, but more importantly you have crossed the hearing threshold and triggered every guard in 330px. Decoys are best used from a low-noise standing position to pull a single guard off your route, not as a panic button.
What we did not do
We deliberately did not give Vault Raid a combat option. There is no takedown key. No silenced weapon. Stealth purists can debate the merits of that choice — we picked it because adding a combat fallback collapses the decision space. If you can punch your way out of a bad noise spike, you stop respecting the noise meter.