feat(ModularBot): stop-shot gun, 10 guns total

- Stop-shot gun: predicts enemy deceleration stop point - Catches bots at direction reversal pauses - Battle-tested vs WaveSurfer, Crazy, RandomMover Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
2026-09-20 01:37:45 +02:00
parent 18ff2d45b3
commit a87be5f99f
2 changed files with 112 additions and 3 deletions
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+## Stop-shot gun: predicts the point where a decelerating enemy will stop.
+## Many bots pause briefly when reversing direction — catches them at the stop.
+## Falls back to linear prediction when enemy is not decelerating.
+## Coordinate system: 0° = East, CCW positive (Tank Royale standard).
+
+import std/math
+import gun_harness/gun_interface
+
+# TR deceleration constants (px/tick²)
+const BrakeDecel = 2.0  ## same-direction stop
+const CoastDecel = 1.0  ## cross-zero coasting stop
+
+type StopShotGun* = object
+  prevSpeed:   float
+  prevHeading: float
+  prevTick:    int
+  frames:      int
+  cachedTick:  int
+  cachedPredX: float
+  cachedPredY: float
+
+proc initStopShotGun*(): StopShotGun = StopShotGun()
+
+proc predict*(g: var StopShotGun, state: WorldState, bulletSpeed: float): GunPrediction =
+  if bulletSpeed <= 0.0:
+    return GunPrediction(x: state.enemyX, y: state.enemyY)
+
+  # Per-tick cache: all power bins share one prediction
+  if state.tick == g.cachedTick:
+    return GunPrediction(x: g.cachedPredX, y: g.cachedPredY)
+
+  defer:
+    g.cachedTick  = state.tick
+    g.cachedPredX = result.x
+    g.cachedPredY = result.y
+
+  # Update history
+  let isNew = state.tick > g.prevTick
+  if isNew:
+    g.prevSpeed   = state.enemySpeed
+    g.prevHeading = state.enemyHeading
+    g.prevTick    = state.tick
+    inc g.frames
+
+  # Need 2+ frames to detect deceleration
+  if g.frames < 2:
+    result = GunPrediction(x: state.enemyX, y: state.enemyY)
+    return
+
+  let speed = state.enemySpeed
+  let prev  = g.prevSpeed
+
+  # Detect deceleration: |speed| is shrinking
+  let decelerating = abs(speed) < abs(prev) and abs(speed) > 0.01
+
+  if not decelerating:
+    # Linear fallback
+    let headRad = degToRad(state.enemyHeading)
+    let dist = hypot(state.enemyX - state.selfX, state.enemyY - state.selfY)
+    let t = dist / bulletSpeed
+    var px = state.enemyX + cos(headRad) * speed * t
+    var py = state.enemyY + sin(headRad) * speed * t
+    result = GunPrediction(
+      x: clamp(px, 0.0, state.arenaWidth),
+      y: clamp(py, 0.0, state.arenaHeight)
+    )
+    return
+
+  # Pick decel rate: braking (speed toward zero on same sign) = 2, else 1
+  # ponytail: simplified; TR has exact rules per direction but this is close enough
+  let decel = if speed * prev > 0.0: BrakeDecel else: CoastDecel
+
+  # Simulate stop position
+  let headRad = degToRad(state.enemyHeading)
+  var v  = speed
+  var sx = state.enemyX
+  var sy = state.enemyY
+  while abs(v) > 0.001:
+    sx += v * cos(headRad)
+    sy += v * sin(headRad)
+    let step = if v > 0.0: -decel else: decel
+    v += step
+    if (v > 0.0) != (speed > 0.0): v = 0.0  # crossed zero
+
+  # Bullet travel time to current pos, check against ticks to stop
+  let dist = hypot(state.enemyX - state.selfX, state.enemyY - state.selfY)
+  let bulletTicks = dist / bulletSpeed
+  let stopTicks   = abs(speed) / decel
+
+  # If bullet arrives well after stop, aim at stop; otherwise linear blend
+  let px = if bulletTicks >= stopTicks: sx else: state.enemyX + cos(headRad) * speed * bulletTicks
+  let py = if bulletTicks >= stopTicks: sy else: state.enemyY + sin(headRad) * speed * bulletTicks
+
+  result = GunPrediction(
+    x: clamp(px, BotRadius, state.arenaWidth  - BotRadius),
+    y: clamp(py, BotRadius, state.arenaHeight - BotRadius)
+  )
+
+proc onResult*(g: var StopShotGun, e: FeedbackEvent) =
+  discard  # analytical gun — no learning