Writing a lane stance

Writing a lane stance

A policy on this cabinet is a prompt. Every 5 seconds the game server hands your seat its own board view and asks for one JSON object; a deterministic autopilot then runs that object 24 times a second for the next 120 ticks. You never touch a joystick — you choose what to go for and how much risk to take.

The reply

{"note": "power pellet 62 ticks away in sw and nothing is chasing me there; take it, then cash the chain",
 "mode": "hunt", "zone": "sw", "risk": 0.55, "lead_ticks": 16,
 "fire": "auto", "say": "going for the power"}

Parsing is tolerant. Markdown fences are stripped; prose before or after the object is ignored (the outermost balanced {…} wins); numeric strings are accepted; a risk above 1 is read as a percentage and divided by 100; mode, zone and fire are matched case-insensitively with synonyms — greedy/collect → clear, attack → strike, chase → hunt, defend/dodge → safe, survive/turtle → bank; "north-west", "top left", "upper left" → nw (and the mirrors), "middle" → centre, "anywhere" → none; "always" → auto, "off" → never.

Only when no usable field at all can be recovered do the single retry and then the scripted fallback fire.

What each mode does

zone multiplies every target outside it by 0.35 — a bias, not a fence.

risk sets the danger gate: a move into a tile whose threat ETA is below (1 - risk) · 96 + 4 ticks is rejected outright. At risk = 0 nothing may come within four tiles; at risk = 1 threats are ignored entirely. In gallery it also decides how early the paddle steps out of a falling bolt's column: a paddle that only dodges in safe dies with a full magazine.

lead_ticks is how long the autopilot commits to a chosen route before re-deciding — but the danger gate can always break a commitment early.

fire matters only in gallery: auto fires whenever a bolt slot and the reload allow, hold fires only when the paddle is lined up on the lowest live marcher in its column, never holds fire.

What you can see

Your own whole screen — every tile, every sprite, your avatar, your lives, your points — plus:

• threats: every hostile in your lane, sorted by eta_ticks ascending;
• targets: up to 12 scoring things, sorted by value / dist_ticks, each with its zone and whether it is safe. This is the same array the autopilot weights, so you are never guessing at a quantity the engine already knows;
• zones: the five fixed regions with their total target value and the soonest a hostile can be in them;
• scoreboard: every rival's alias, score, lives and screen — the entire cross-lane surface, and read-only.

You cannot see any other lane's board, sprites, stance, note or policy, the seed, any RNG state, any future draw, any wall-clock fact, or who holds any seat, including your own.

Two worked stances

Cash a chain. power_ticks_left is above 60, so the four hunters are fleeing for another 2.5 seconds and the chain pays 100 + 150 + 200 + 250:

{"note": "power window open with 2.5s left; three hunters within 5 tiles",
 "mode": "strike", "zone": "none", "risk": 0.85, "lead_ticks": 10,
 "fire": "auto", "say": "chain time"}

Protect a lead. You are ahead on the scoreboard with 25 seconds left; a life is worth 1.000 and 200 more points are worth 2.000, but a death costs 1.000 and the clock:

{"note": "leading by 4.2 with 25s left; nothing is worth a life now",
 "mode": "bank", "zone": "none", "risk": 0.1, "lead_ticks": 12,
 "fire": "auto", "say": "sitting on it"}

The published baselines

Both ship in the same image and emit the identical object, so they are directly comparable with any prompt.

arcader (PLAYER_SCRIPTED=arcader) — the certification player, the per-turn fallback and the default for a seat that registers with neither env var:

1. lane over → safe, risk 0, fire: never;
2. else powerTicksLeft > 48 → strike, risk 0.85, lead 10;
3. else the nearest threat inside panicTicks (20) → safe, risk 0.15, lead 8;
4. else a power pellet within 72 ticks → hunt in that pellet's zone, lead 16;
5. else clear in the zone with the most target value;
6. and in every branch, on the last life: halve the risk and demote hunt to clear.

hoover (PLAYER_SCRIPTED=hoover) — deliberately different in shape and weaker: {"mode":"clear","zone":"none","risk":1.0,"lead_ticks":24, "fire":"auto"} every turn. It never dodges. It banks points fast and dies fast, which gives the ladder a spread.

arcader's three tunables (panicTicks, riskMilli, leadTicks) are a BaselineParams object rather than literals because they were chosen by a grid sweep, not guessed: tools/tune_baselines.nim plays four arcaders over a 4 × 3 × 3 matrix across all three ROMs and six seeds, tools/ci/baseline_tuning.json records the whole grid and the pick, and tests/test_tuning.nim re-asserts that the shipped defaults still equal it.