From c0abd4c960c25984825c96d69146b67bd66a344e Mon Sep 17 00:00:00 2001
From: Davide Cappellini <signorsasso@gmail.com>
Date: Sun, 20 Sep 2026 10:44:49 +0200
Subject: [PATCH] =?UTF-8?q?feat(ModularBot):=20virtual=20body=20movement?=
 =?UTF-8?q?=20selector=20=E2=80=94=20wave-based=20scoring=20replaces=20EMA?=
 =?UTF-8?q?=20damage?=
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Implements VirtualBodyTracker (wave-based hit/miss scoring) instead of EMA damage accumulation. Movement switching now happens every tick, not every 3 rounds. Also refactors radar colors to dark teal (#004444/#0D4D4D) for faint visibility.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 ModularBot_garage/src/ModularBot.nim          |  54 +++----
 .../movement_harness/virtual_bodies.nim       | 152 ++++++++++++++++++
 2 files changed, 176 insertions(+), 30 deletions(-)
 create mode 100644 common_libs/movement_harness/virtual_bodies.nim

diff --git a/ModularBot_garage/src/ModularBot.nim b/ModularBot_garage/src/ModularBot.nim
index 4e4ec1d..4479808 100644
--- a/ModularBot_garage/src/ModularBot.nim
+++ b/ModularBot_garage/src/ModularBot.nim
@@ -25,6 +25,7 @@ import guns/averaged_lead
 import guns/decay_gf
 import movements/phantom_meteor
 import movements/wave_surfer
+import movement_harness/virtual_bodies as mvb
 
 const botJsonPath = currentSourcePath().parentDir / "ModularBot.json"
 const DebugVBullets = false
@@ -54,10 +55,7 @@ type
     mover:        PhantomMeteorModule
     waveMover:    WaveSurferModule
     movementId:   int    ## 0=phantom, 1=waveSurf
-    dmgPhantom:   float  ## rolling damage taken under phantom
-    dmgWaveSurf:  float  ## rolling damage taken under waveSurf
-    roundDmg:     float  ## damage this round
-    roundCount:   int
+    moveTracker:  VirtualBodyTracker
     virtualHits:  int
     virtualMiss:  int
     tick:         int
@@ -215,35 +213,25 @@ method onScannedBot*(bot: ModularBot, e: ScannedBotEvent) =
 
 
 method onHitByBullet*(bot: ModularBot, e: HitByBulletEvent) =
-  bot.roundDmg += e.damage
+  bot.moveTracker.registerHit(e.bullet.power, e.bullet.direction, getX(), getY())
 
 method onRoundEnded*(bot: ModularBot, e: RoundEndedEventForBot) =
-  # Accumulate damage into active movement bucket (exponential decay, α=0.5)
-  # ponytail: simple EMA; switch to longer window if thrashing becomes a problem
-  let decay = 0.5
-  if bot.movementId == 0:
-    bot.dmgPhantom  = decay * bot.dmgPhantom  + (1.0 - decay) * bot.roundDmg
-  else:
-    bot.dmgWaveSurf = decay * bot.dmgWaveSurf + (1.0 - decay) * bot.roundDmg
-  echo "[move] round dmg=", bot.roundDmg, " phantom_ema=", bot.dmgPhantom, " wave_ema=", bot.dmgWaveSurf
+  let newId = bot.moveTracker.bestMovement()
+  if newId != bot.movementId:
+    echo "[move] switching: ", (if newId == 0: "phantom_meteor" else: "wave_surfer")
+    bot.movementId = newId
 
 method onRoundStarted*(bot: ModularBot, e: RoundStartedEvent) =
   setAdjustGunForBodyTurn(true)
   setAdjustRadarForBodyTurn(true)
   setAdjustRadarForGunTurn(true)
-  setRadarColor("#00CCCC")  # RadarLock: cyan/teal
-  setScanColor("#33FFFF")   # RadarLock scan arc: bright teal
+  setRadarColor("#004444")  # RadarLock: dark teal, faint without alpha
+  setScanColor("#0D4D4D")   # RadarLock scan arc: very dark teal, faint without alpha
   bot.radar.init()
   bot.hasContact = false
   bot.tick       = 0
   bot.currentGun = -1
-  bot.roundDmg   = 0.0
-  inc bot.roundCount
-
-  # Every 3 rounds: switch to lower-damage movement (probe every 3rd round)
-  # ponytail: simple 3-round probe; add hysteresis if switching thrashes
-  if bot.roundCount > 2:
-    bot.movementId = if bot.dmgPhantom <= bot.dmgWaveSurf: 0 else: 1
+  bot.moveTracker.resetRound(getX(), getY(), getDirection(), getSpeed())
 
   if bot.movementId == 0:
     bot.mover.resetRound()
@@ -271,10 +259,15 @@ method run*(bot: ModularBot) =
       go()
       continue
 
-    # Movement harness: dispatch to active mover
-    let (spd, tr) =
-      if bot.movementId == 0: bot.mover.computeMove(bot.lastState)
-      else: bot.waveMover.computeMove(bot.lastState)
+    # Movement harness: compute all, feed tracker, apply active
+    let phantomCmd  = bot.mover.computeMove(bot.lastState)
+    let waveSurfCmd = bot.waveMover.computeMove(bot.lastState)
+    bot.moveTracker.tick(bot.lastState, [phantomCmd, waveSurfCmd])
+    let activeId = bot.moveTracker.bestMovement()
+    if activeId != bot.movementId:
+      bot.movementId = activeId
+      echo "[move] switched to: ", (if activeId == 0: "phantom_meteor" else: "wave_surfer")
+    let (spd, tr) = if bot.movementId == 0: phantomCmd else: waveSurfCmd
     setTargetSpeed(spd)
     setTurnRate(tr)
 
@@ -297,9 +290,10 @@ when isMainModule:
     displace:    initDisplacementGun(),
     avgLead:     initAveragedLeadGun(),
     decayGF:     initDecayGFGun(),
-    radar:      RadarLockModule(),
-    mover:      initPhantomMeteor(),
-    waveMover:  initWaveSurfer(),
-    currentGun: -1,
+    radar:        RadarLockModule(),
+    mover:        initPhantomMeteor(),
+    waveMover:    initWaveSurfer(),
+    moveTracker:  mvb.initVirtualBodyTracker(2),  # 0=phantom, 1=waveSurf
+    currentGun:   -1,
   )
   start(bot, botJsonPath)
diff --git a/common_libs/movement_harness/virtual_bodies.nim b/common_libs/movement_harness/virtual_bodies.nim
new file mode 100644
index 0000000..cf01f6b
--- /dev/null
+++ b/common_libs/movement_harness/virtual_bodies.nim
@@ -0,0 +1,152 @@
+## Virtual body tracker — mirrors virtual_bullets.nim but for movement modules.
+## Tracks simulated positions for each movement candidate under enemy waves.
+## Scores modules by how often they sit in high-danger GF bins.
+## Caller feeds actual hit data via registerHit() to build the danger profile.
+
+import std/math
+import gun_harness/gun_interface
+import movement_harness/movement_interface
+
+const
+  VB_BINS*     = 31      ## GF bins from -1 to +1
+  MaxWaves*    = 64      ## hard cap; ponytail: ring buffer, resize if needed
+  MaxModules*  = 8       ## max movement modules tracked
+
+type
+  VBWave = object
+    fireX, fireY:    float
+    fireBearingRad:  float   ## bearing from fireOrigin to REAL bot at fire time (radians)
+    speed:           float
+    radius:          float
+    fireTick:        int
+    startDist:       float
+
+  VirtualBody = object
+    x, y:     float
+    heading:  float   ## degrees (Tank Royale / bot API)
+    speed:    float   ## current speed px/tick
+
+  VirtualBodyTracker* = object
+    numModules:    int
+    bodies:        array[MaxModules, VirtualBody]
+    dangerScore:   array[MaxModules, float]       ## accumulated danger hits
+    dangerBins:    array[VB_BINS, float]          ## populated from registerHit
+    waves:         array[MaxWaves, VBWave]
+    waveCount:     int
+    waveHead:      int  ## ring buffer head
+    prevEnemyEnergy: float
+    arenaW, arenaH: float
+
+proc initVirtualBodyTracker*(numModules: int): VirtualBodyTracker =
+  result.numModules       = numModules
+  result.prevEnemyEnergy  = 100.0
+  # Seed bins so we have a uniform prior before any real hits
+  for i in 0..<VB_BINS: result.dangerBins[i] = 1.0
+
+proc resetRound*(t: var VirtualBodyTracker, startX, startY, startHeading, startSpeed: float) =
+  ## Reset virtual body positions to actual bot position at round start.
+  for i in 0..<t.numModules:
+    t.bodies[i] = VirtualBody(x: startX, y: startY,
+                               heading: startHeading, speed: startSpeed)
+  t.waveCount          = 0
+  t.waveHead           = 0
+  t.prevEnemyEnergy    = 100.0
+
+proc registerHit*(t: var VirtualBodyTracker, bulletPower: float, bulletHeadingDeg: float,
+                  realX, realY: float) =
+  ## Feed an actual HitByBullet event in. Computes exact GF bin and increments danger.
+  ## bulletHeadingDeg: the heading the bullet was travelling when it hit (degrees).
+  ## We need the wave that fired it to get fireBearing; absent that, just increment center.
+  ## ponytail: approximate — we don't correlate to exact wave here, just record impact direction.
+  ## The bearing the bullet came FROM reversed = direction from fireOrigin to us at impact.
+  ## Without access to the wave origin we use a weight-1 spike at center bin.
+  ## TODO: correlate to nearest wave for exact GF if needed.
+  let centerBin = VB_BINS div 2
+  t.dangerBins[centerBin] += 2.0  # spike center on real hit
+
+proc gfToBin(gf: float): int {.inline.} =
+  clamp(int(round((gf.clamp(-1.0, 1.0) + 1.0) * 0.5 * float(VB_BINS - 1))), 0, VB_BINS - 1)
+
+proc mea(speed: float): float {.inline.} = arcsin(min(8.0 / speed, 1.0))
+
+proc advanceBody(b: var VirtualBody, cmd: MoveCommand, arenaW, arenaH: float) =
+  ## Single-tick physics: apply MoveCommand, clamp to arena.
+  let (targetSpeed, desiredTurn) = cmd
+  # maxTurnRate depends on current speed (Tank Royale formula)
+  let maxTurn = 10.0 - 0.75 * abs(b.speed)
+  b.heading += clamp(desiredTurn, -maxTurn, maxTurn)
+  # Speed ramps ±1 toward target, clamped to [-8, 8]
+  let tgt = clamp(targetSpeed, -8.0, 8.0)
+  if b.speed < tgt:
+    b.speed = min(b.speed + 1.0, tgt)
+  else:
+    b.speed = max(b.speed - 1.0, tgt)
+  let headingRad = degToRad(b.heading)
+  b.x += b.speed * cos(headingRad)
+  b.y += b.speed * sin(headingRad)
+  b.x = clamp(b.x, 18.0, arenaW - 18.0)
+  b.y = clamp(b.y, 18.0, arenaH - 18.0)
+
+proc tick*[N: static int](t: var VirtualBodyTracker, state: WorldState,
+                           cmds: array[N, MoveCommand]) =
+  ## Per-tick update. cmds[i] is computeMove() output of module i.
+  ## Call AFTER collecting all module commands for this tick.
+
+  # --- Fire detection ---
+  let drop = t.prevEnemyEnergy - state.enemyEnergy
+  t.prevEnemyEnergy = state.enemyEnergy
+  if drop >= 0.1 and drop <= 3.0:
+    let bspeed = 20.0 - 3.0 * drop
+    let bearingRad = arctan2(state.selfY - state.enemyY, state.selfX - state.enemyX)
+    let d = hypot(state.selfX - state.enemyX, state.selfY - state.enemyY)
+    let slot = t.waveHead mod MaxWaves
+    t.waves[slot] = VBWave(
+      fireX:        state.enemyX,
+      fireY:        state.enemyY,
+      fireBearingRad: bearingRad,
+      speed:        bspeed,
+      radius:       0.0,
+      fireTick:     state.tick,
+      startDist:    d,
+    )
+    t.waveHead = (t.waveHead + 1) mod MaxWaves
+    if t.waveCount < MaxWaves: inc t.waveCount
+
+  # --- Advance virtual bodies ---
+  for i in 0..<t.numModules:
+    when N > MaxModules:
+      {.error: "cmds array exceeds MaxModules".}
+    if i < N:
+      advanceBody(t.bodies[i], cmds[i], state.arenaWidth, state.arenaHeight)
+
+  # --- Advance waves and score ---
+  # ponytail: O(waves * modules), small counts, fine
+  for wi in 0..<t.waveCount:
+    let idx = wi mod MaxWaves
+    var w = addr t.waves[idx]
+    if w.speed <= 0.0: continue
+    w.radius += w.speed
+    for mi in 0..<t.numModules:
+      let bx = t.bodies[mi].x
+      let by = t.bodies[mi].y
+      let d = hypot(bx - w.fireX, by - w.fireY)
+      # Wave crosses virtual body: within BotRadius of its current position
+      if abs(w.radius - d) <= BotRadius:
+        let toBotRad = arctan2(by - w.fireY, bx - w.fireX)
+        var off = toBotRad - w.fireBearingRad
+        while off >  PI: off -= 2.0 * PI
+        while off < -PI: off += 2.0 * PI
+        let maxA = mea(w.speed)
+        if maxA >= 1e-9:
+          let gf = clamp(off / maxA, -1.0, 1.0)
+          let bin = gfToBin(gf)
+          t.dangerScore[mi] += t.dangerBins[bin]
+
+proc bestMovement*(t: VirtualBodyTracker): int =
+  ## Returns index of module with lowest accumulated danger score.
+  result = 0
+  var best = t.dangerScore[0]
+  for i in 1..<t.numModules:
+    if t.dangerScore[i] < best:
+      best = t.dangerScore[i]
+      result = i