app.js

;(function () {
  'use strict'

  function $(id) {
    return document.getElementById(id)
  }

  function svgEl(tag, attrs) {
    var el = document.createElementNS('http://www.w3.org/2000/svg', tag)
    if (attrs) for (var k in attrs) el.setAttribute(k, attrs[k])
    return el
  }

  function rgba(triplet, alpha) {
    return 'rgba(' + triplet + ',' + alpha + ')'
  }

  var svg = null
  var wrap = null
  var W = 0
  var H = 0
  var camCX = 0
  var camCY = 0
  var SCALE = 0
  var zoomLevel = 1.0
  /** World km from camera to farthest canvas corner when zoom label = 100%; +/- zoom scales this radius. */
  var BASE_VIEW_RADIUS_KM = 1.5
  /** Keeps map labels readable vs panel type (~15% bump; pair with .coastal-surveillance-sim font-size). */
  var MAP_LABEL_SCALE = 1.15

  var worldG = null
  var bgSky = null
  var bgSea = null
  var horizLine = null
  var ringsG = null
  var compassG = null
  var zonesG = null

  var dynamicCamG = null
  var coneEl = null
  var camPointer = null
  var camDot = null
  var camCorners = []
  var boatG = null
  var boatHalo = null
  var boatIconG = null
  var boatIconScaleG = null
  var boatHull = null
  var trajLine = null
  var boatTrail = null
  var bearingLine = null

  var anchorSOuter = null
  var anchorS = null
  var anchorEOuter = null
  var anchorE = null
  var anchorSLabel = null
  var anchorELabel = null

  var trailFlat = []
  var TRAIL_CAP = 100
  var TRAIL_MIN_DIST = 0.0028
  /** Min blind+detected metres before showing blind share (avoids noisy % on tiny streaks). */
  var MIN_BLIND_SHARE_M = 10
  var lastTrailIconAngle = NaN

  var FONT_SANS = 'Saira Condensed, Arial Narrow, Arial, sans-serif'
  var statCache = {}

  var lastTrackSx = NaN
  var lastTrackSy = NaN
  var lastTrackEx = NaN
  var lastTrackEy = NaN
  var lastDrawScale = NaN
  var prevInFov = null

  var boatStart = { x: 0.0, y: 1.0 }
  var boatEnd = { x: 0.0, y: 0.15 }
  var dragging = null
  var camHeading = 0
  var boatT = 0
  var boatDir = 1
  var lastTime = null

  var prevVisible = null
  var detectedStreak = 0
  var blindStreak = 0
  var lastDetectedStreak = 0
  var lastBlindStreak = 0
  var prevDetectedStreak = 0
  var prevBlindStreak = 0

  var lastPinchDist = null
  var running = false
  var camDir = -1

  var inpFov = null
  var inpFrontSpeed = null
  var inpBackSpeed = null
  var inpFrontArc = null
  var inpBoatSpeed = null

  var cachedConeFov = NaN
  var cachedConeR = NaN
  var cachedPtrLen = NaN

  var lastDrawBx = NaN
  var lastDrawBy = NaN

  var hitL = 0
  var hitT = 0
  var hitSx = 1
  var hitSy = 1

  var resizeRaf = 0
  var panelStatsRaf = 0
  var panelStatsPayload = null
  var zoomVisualRaf = 0

  var C = {
    p: '', d: '', s: '', w: '', s1: '', s2: '',
    pr: '', dr: '', sr: '', wr: '',
    pc: '', dc: '', sc: '', wc: '', hi: '', lo: '',
  }

  var systemQuery = window.matchMedia('(prefers-color-scheme: light)')

  function loadColors() {
    var cs = getComputedStyle(document.querySelector('.coastal-surveillance-sim'))
    function v(n) { return cs.getPropertyValue(n).trim() }
    C.p = v('--primary'); C.d = v('--danger'); C.s = v('--success'); C.w = v('--warning')
    C.s1 = v('--surface-1'); C.s2 = v('--surface-2')
    C.pr = v('--primary-rgb'); C.dr = v('--danger-rgb'); C.sr = v('--success-rgb'); C.wr = v('--warning-rgb')
    C.pc = v('--primary-content'); C.dc = v('--danger-content'); C.sc = v('--success-content'); C.wc = v('--warning-content')
    C.hi = v('--content-hi'); C.lo = v('--content-lo')
    if (horizLine) horizLine.setAttribute('stroke', rgba(C.pr, 0.4))
    if (zoomVisualRaf) { cancelAnimationFrame(zoomVisualRaf); zoomVisualRaf = 0 }
    buildWorldElements()
    buildZones()
    prevInFov = null
    syncThemedSceneStrokes()
    if (panelStatsRaf) { cancelAnimationFrame(panelStatsRaf); panelStatsRaf = 0 }
    panelStatsPayload = null
  }

  function initTheme() {
    var btns = document.querySelectorAll('.theme-btn')
    function applyTheme(pref) {
      var sim = document.querySelector('.coastal-surveillance-sim')
      sim.dataset.theme = pref === 'system' ? (systemQuery.matches ? 'light' : 'dark') : pref
      loadColors()
      for (var i = 0; i < btns.length; i++)
        btns[i].classList.toggle('active', btns[i].dataset.themeVal === pref)
    }
    applyTheme(localStorage.getItem('theme') || 'system')
    systemQuery.addEventListener('change', function () {
      if (localStorage.getItem('theme') === 'system') applyTheme('system')
    })
    for (var j = 0; j < btns.length; j++)
      btns[j].addEventListener('click', function () {
        localStorage.setItem('theme', this.dataset.themeVal)
        applyTheme(this.dataset.themeVal)
      })
  }

  function resetStreaks() {
    detectedStreak = blindStreak = lastDetectedStreak = lastBlindStreak = 0
    prevDetectedStreak = prevBlindStreak = prevVisible = null
  }


  function clearTrail(resetIconAngle) {
    trailFlat.length = 0
    if (resetIconAngle !== false) lastTrailIconAngle = NaN
    if (boatTrail) boatTrail.setAttribute('points', '')
  }

  function flushTrailPoly() {
    if (!boatTrail || !trailFlat.length) return
    var s = trailFlat[0] + ',' + trailFlat[1]
    for (var i = 2; i < trailFlat.length; i += 2)
      s += ' ' + trailFlat[i] + ',' + trailFlat[i + 1]
    boatTrail.setAttribute('points', s)
  }

  function appendTrail(bx, by) {
    var m = trailFlat.length
    if (m >= 2) {
      var lx = trailFlat[m - 2]
      var ly = trailFlat[m - 1]
      if (Math.hypot(bx - lx, by - ly) < TRAIL_MIN_DIST) return
    }
    trailFlat.push(bx, by)
    while (trailFlat.length > TRAIL_CAP * 2) {
      trailFlat.shift()
      trailFlat.shift()
    }
    flushTrailPoly()
  }

  function sectorPath(fromDeg, toDeg, R, maxSteps) {
    var span = ((toDeg - fromDeg) + 360) % 360
    var steps = Math.ceil(span / 2)
    steps = maxSteps != null && maxSteps > 0
      ? Math.max(4, Math.min(maxSteps, Math.max(steps, 4)))
      : Math.max(64, steps)
    var d = 'M 0 0'
    for (var i = 0; i <= steps; i++) {
      var deg = fromDeg + (span / steps) * i
      var rad = deg * Math.PI / 180
      d += ' L ' + (Math.sin(rad) * R) + ' ' + (Math.cos(rad) * R)
    }
    return d + ' Z'
  }

  function zoneFillRadiusWorld() {
    if (SCALE === 0) return 0.1
    function distWorld(px, py) {
      return Math.hypot((px - camCX) / SCALE, (camCY - py) / SCALE)
    }
    return Math.max(Math.max(distWorld(0, 0), distWorld(W, 0), distWorld(W, H), distWorld(0, H)) * 1.08, 0.04)
  }

  function coneRadiusWorld() {
    if (SCALE === 0) return 0.1
    return Math.max(zoneFillRadiusWorld(), Math.hypot(W, H) / SCALE * 1.12)
  }

  function syncConeAndPointerShape(p) {
    if (!coneEl || SCALE === 0) return
    var fov = p ? p.fov : +inpFov.value
    var R = coneRadiusWorld()
    var ptrLen = 32 / SCALE
    if (fov === cachedConeFov && Math.abs(R - cachedConeR) < 1e-6 && Math.abs(ptrLen - cachedPtrLen) < 1e-12) return
    cachedConeFov = fov
    cachedConeR = R
    cachedPtrLen = ptrLen
    var half = fov / 2
    coneEl.setAttribute('d', sectorPath(-half, half, R, 22))
    camPointer.setAttribute('x2', 0)
    camPointer.setAttribute('y2', ptrLen)
  }

  function syncThemedSceneStrokes() {
    if (!coneEl) return
    coneEl.setAttribute('fill', rgba(C.pr, 0.12))
    coneEl.setAttribute('stroke', rgba(C.pr, 0.6))
    camPointer.setAttribute('stroke', rgba(C.pr, 0.9))
    camDot.setAttribute('fill', C.p)
    camDot.setAttribute('stroke', rgba(C.pr, 0.5))
    trajLine.setAttribute('stroke', rgba(C.dr, 0.25))
    bearingLine.setAttribute('stroke', rgba(C.dr, 0.12))
    if (boatTrail) boatTrail.setAttribute('stroke', rgba(C.dr, 0.55))
    for (var i = 0; i < 4; i++) camCorners[i].setAttribute('stroke', rgba(C.pr, 0.5))
    anchorSOuter.setAttribute('stroke', rgba(C.dr, 0.72))
    anchorS.setAttribute('fill', rgba(C.dr, 0.52))
    anchorS.setAttribute('stroke', rgba(C.dr, 0.45))
    anchorEOuter.setAttribute('stroke', rgba(C.wr, 0.72))
    anchorE.setAttribute('fill', rgba(C.wr, 0.48))
    anchorE.setAttribute('stroke', rgba(C.wr, 0.42))
    anchorSLabel.setAttribute('fill', rgba(C.dr, 0.88))
    anchorELabel.setAttribute('fill', rgba(C.wr, 0.88))
  }

  function updateTrackSvgGeomIfNeeded() {
    if (boatStart.x === lastTrackSx && boatStart.y === lastTrackSy &&
        boatEnd.x === lastTrackEx && boatEnd.y === lastTrackEy) return
    if (!isNaN(lastTrackSx)) clearTrail()
    lastTrackSx = boatStart.x
    lastTrackSy = boatStart.y
    lastTrackEx = boatEnd.x
    lastTrackEy = boatEnd.y
    trajLine.setAttribute('x1', boatStart.x)
    trajLine.setAttribute('y1', boatStart.y)
    trajLine.setAttribute('x2', boatEnd.x)
    trajLine.setAttribute('y2', boatEnd.y)
    anchorSOuter.setAttribute('cx', boatStart.x)
    anchorSOuter.setAttribute('cy', boatStart.y)
    anchorS.setAttribute('cx', boatStart.x)
    anchorS.setAttribute('cy', boatStart.y)
    anchorEOuter.setAttribute('cx', boatEnd.x)
    anchorEOuter.setAttribute('cy', boatEnd.y)
    anchorE.setAttribute('cx', boatEnd.x)
    anchorE.setAttribute('cy', boatEnd.y)
    var syOff = 14 * MAP_LABEL_SCALE / SCALE
    anchorSLabel.setAttribute('x', boatStart.x)
    anchorSLabel.setAttribute('y', -(boatStart.y - syOff))
    anchorELabel.setAttribute('x', boatEnd.x)
    anchorELabel.setAttribute('y', -(boatEnd.y - syOff))
  }

  function updateScaleOnlySvgGeom() {
    var cr = 8 / SCALE
    var cornerPx = 14 / SCALE
    camDot.setAttribute('r', cr)
    for (var ci = 0; ci < 4; ci++) {
      var wx = (ci === 0 || ci === 3 ? -1 : 1) * cornerPx
      var wy = (ci < 2 ? 1 : -1) * cornerPx
      camCorners[ci].setAttribute('x1', wx * 0.4)
      camCorners[ci].setAttribute('y1', wy * 0.4)
      camCorners[ci].setAttribute('x2', wx)
      camCorners[ci].setAttribute('y2', wy)
    }
    var rHit = 6 / SCALE
    var rRing = 10 / SCALE
    anchorS.setAttribute('r', rHit)
    anchorSOuter.setAttribute('r', rRing)
    anchorE.setAttribute('r', rHit)
    anchorEOuter.setAttribute('r', rRing)
    boatHalo.setAttribute('r', 22 / SCALE)
    var fsA = 11 * MAP_LABEL_SCALE / SCALE
    anchorSLabel.setAttribute('font-size', fsA)
    anchorELabel.setAttribute('font-size', fsA)
    var iconPx = 15 / SCALE
    boatIconScaleG.setAttribute('transform', 'scale(' + iconPx + ')')
    syncConeAndPointerShape(null)
    lastTrackSx = NaN
  }

  function buildLineZone(x1, y1, x2, y2) {
    return svgEl('line', {
      x1: x1, y1: y1, x2: x2, y2: y2,
      stroke: rgba(C.pr, 0.5), 'stroke-width': 1, 'stroke-dasharray': '5 5',
      'vector-effect': 'non-scaling-stroke',
    })
  }

  function buildZones() {
    if (!zonesG || SCALE === 0) return
    while (zonesG.firstChild) zonesG.removeChild(zonesG.firstChild)
    var frontArc = +inpFrontArc.value
    var fh = frontArc / 2
    var R = zoneFillRadiusWorld()
    zonesG.appendChild(svgEl('path', { d: sectorPath(-fh, fh, R), fill: rgba(C.pr, 0.07), stroke: 'none' }))
    zonesG.appendChild(svgEl('path', { d: sectorPath(fh, 360 - fh, R), fill: rgba(C.dr, 0.06), stroke: 'none' }))
    var e1r = (-fh) * Math.PI / 180
    var e2r = fh * Math.PI / 180
    zonesG.appendChild(buildLineZone(0, 0, Math.sin(e1r) * R, Math.cos(e1r) * R))
    zonesG.appendChild(buildLineZone(0, 0, Math.sin(e2r) * R, Math.cos(e2r) * R))
    var labelR = 80 / SCALE
    var fs = 11 * MAP_LABEL_SCALE / SCALE
    var tf = svgEl('text', { x: 0, y: -labelR, transform: 'scale(1,-1)',
      fill: C.pc, 'font-size': fs, 'font-family': FONT_SANS, 'text-anchor': 'middle' })
    tf.textContent = 'FRONT ' + frontArc + '\u00b0'
    zonesG.appendChild(tf)
    var tb = svgEl('text', { x: 0, y: 18 * MAP_LABEL_SCALE / SCALE, transform: 'scale(1,-1)',
      fill: C.dc, 'font-size': fs, 'font-family': FONT_SANS, 'text-anchor': 'middle' })
    tb.textContent = 'BACK ' + (360 - frontArc) + '\u00b0'
    zonesG.appendChild(tb)
    var edgeTxt = '\u00b1' + fh.toFixed(0) + '\u00b0'
    for (var ei = 0; ei < 2; ei++) {
      var rad = ei ? e2r : e1r
      var tx = svgEl('text', {
        x: Math.sin(rad) * labelR, y: -(Math.cos(rad) * labelR),
        transform: 'scale(1,-1)', fill: C.lo,
        'font-size': fs, 'font-family': FONT_SANS, 'text-anchor': 'middle',
      })
      tx.textContent = edgeTxt
      zonesG.appendChild(tx)
    }
  }

  function fmtDist(d) {
    return d < 1 ? Math.round(d * 1000) + 'm' : d.toFixed(d < 10 ? 2 : 1).replace(/\.0+$/, '') + 'km'
  }

  function buildWorldElements() {
    if (!ringsG || !compassG || SCALE === 0) return
    while (ringsG.firstChild) ringsG.removeChild(ringsG.firstChild)
    var nice = [0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1.0, 2.0, 5.0]
    var ringInterval = nice[0]
    for (var i = 0; i < nice.length; i++) {
      var px = nice[i] * SCALE
      if (px >= 100 && px <= 240) { ringInterval = nice[i]; break }
      if (px < 100) ringInterval = nice[i]
    }
    var maxDist = viewportMaxCornerPx() / SCALE
    var maxRing = Math.ceil(maxDist / ringInterval) + 1
    var fs = 12 * MAP_LABEL_SCALE / SCALE
    var tw = 5 / SCALE
    for (var ri = 1; ri <= maxRing; ri++) {
      var r = ri * ringInterval
      ringsG.appendChild(svgEl('circle', { cx: 0, cy: 0, r: r, fill: 'none',
        stroke: rgba(C.pr, 0.25), 'stroke-width': 0.5, 'vector-effect': 'non-scaling-stroke' }))
      ringsG.appendChild(svgEl('line', { x1: -tw, y1: r, x2: tw, y2: r,
        stroke: rgba(C.pr, 0.7), 'stroke-width': 1, 'vector-effect': 'non-scaling-stroke' }))
      var lbl = svgEl('text', { x: 8 * MAP_LABEL_SCALE / SCALE, y: -r, transform: 'scale(1,-1)',
        fill: C.pc, 'font-size': fs, 'font-family': FONT_SANS })
      lbl.textContent = fmtDist(r)
      ringsG.appendChild(lbl)
    }

    while (compassG.firstChild) compassG.removeChild(compassG.firstChild)
    var compassR = Math.min(camCX * 0.88, camCY * 0.92) / SCALE
    var fsC = 11 * MAP_LABEL_SCALE / SCALE
    compassG.appendChild(svgEl('line', { x1: 0, y1: 0, x2: 0, y2: compassR + 20 / SCALE,
      stroke: rgba(C.pr, 0.2), 'stroke-width': 0.5, 'stroke-dasharray': (4 / SCALE) + ' ' + (4 / SCALE),
      'vector-effect': 'non-scaling-stroke' }))
    for (var deg = 0; deg < 360; deg += 10) {
      var maj = deg % 30 === 0
      var rad = deg * Math.PI / 180
      var wx0 = Math.sin(rad) * compassR
      var wy0 = Math.cos(rad) * compassR
      var tlen = (maj ? 8 : 4) / SCALE
      compassG.appendChild(svgEl('line', {
        x1: wx0, y1: wy0, x2: Math.sin(rad) * (compassR + tlen), y2: Math.cos(rad) * (compassR + tlen),
        stroke: rgba(C.pr, maj ? 0.65 : 0.35),
        'stroke-width': maj ? 1 : 0.5,
        'vector-effect': 'non-scaling-stroke',
      }))
      if (maj) {
        var lr = compassR + (8 + 10) * MAP_LABEL_SCALE / SCALE
        var t = svgEl('text', { x: Math.sin(rad) * lr, y: -Math.cos(rad) * lr, transform: 'scale(1,-1)',
          fill: C.lo, 'font-size': fsC, 'font-family': FONT_SANS, 'text-anchor': 'middle', 'dominant-baseline': 'middle' })
        t.textContent = deg + '\u00b0'
        compassG.appendChild(t)
      }
    }
  }

  function updateWorldTransform() {
    if (worldG) worldG.setAttribute('transform',
      'translate(' + camCX + ',' + camCY + ') scale(' + SCALE + ',' + (-SCALE) + ')')
  }

  function refreshSvgHitBox() {
    if (!svg || W <= 0 || H <= 0) return
    var r = svg.getBoundingClientRect()
    if (r.width < 1 || r.height < 1) return
    hitL = r.left
    hitT = r.top
    hitSx = W / r.width
    hitSy = H / r.height
  }

  function rebuildWorldSvg() {
    buildWorldElements()
    buildZones()
    if (coneEl && SCALE > 0) {
      updateScaleOnlySvgGeom()
      lastDrawScale = SCALE
    }
    refreshSvgHitBox()
  }

  function viewportMaxCornerPx() {
    if (W <= 0 || H <= 0) return 1
    return Math.max(
      Math.hypot(camCX, camCY),
      Math.hypot(W - camCX, camCY),
      Math.hypot(camCX, H - camCY),
      Math.hypot(W - camCX, H - camCY)
    )
  }

  function resize() {
    if (!svg || !wrap) return
    W = wrap.clientWidth
    H = wrap.clientHeight
    svg.setAttribute('width', W)
    svg.setAttribute('height', H)
    camCX = W / 2
    camCY = H * 0.9
    SCALE = viewportMaxCornerPx() / BASE_VIEW_RADIUS_KM * zoomLevel
    updateWorldTransform()
    if (bgSky) { bgSky.setAttribute('width', W); bgSky.setAttribute('height', camCY) }
    if (bgSea) { bgSea.setAttribute('y', camCY); bgSea.setAttribute('width', W); bgSea.setAttribute('height', H - camCY) }
    if (horizLine) { horizLine.setAttribute('x2', W); horizLine.setAttribute('y1', camCY); horizLine.setAttribute('y2', camCY) }
    rebuildWorldSvg()
  }

  function updateZoomLabel() {
    var el = $('zoom-label')
    if (el) el.textContent = Math.round(zoomLevel * 100) + '%'
  }

  function flushZoomVisuals() {
    zoomVisualRaf = 0
    if (!svg || SCALE <= 0) return
    updateWorldTransform()
    rebuildWorldSvg()
  }

  function scheduleZoomVisuals() {
    if (!zoomVisualRaf) zoomVisualRaf = requestAnimationFrame(flushZoomVisuals)
  }

  function applyZoom(delta) {
    var factor = delta > 0 ? 1.12 : 1 / 1.12
    zoomLevel = Math.max(0.3, Math.min(8, zoomLevel * factor))
    SCALE = viewportMaxCornerPx() / BASE_VIEW_RADIUS_KM * zoomLevel
    scheduleZoomVisuals()
    updateZoomLabel()
  }

  function getParams() {
    return {
      fov: +inpFov.value,
      frontSpeed: +inpFrontSpeed.value,
      backSpeed: +inpBackSpeed.value,
      frontArc: +inpFrontArc.value,
      boatSpeed: +inpBoatSpeed.value,
    }
  }

  function worldToCanvas(wx, wy) {
    return { x: camCX + wx * SCALE, y: camCY - wy * SCALE }
  }

  function canvasToWorld(cx, cy) {
    return { x: (cx - camCX) / SCALE, y: (camCY - cy) / SCALE }
  }

  function isFront(heading, arc) {
    var h = ((heading % 360) + 360) % 360
    if (h > 180) h -= 360
    return Math.abs(h) <= arc / 2
  }

  function setDir(d) {
    camDir = d
    var cw = $('dir-cw')
    var ccw = $('dir-ccw')
    if (cw) cw.classList.toggle('active', d === 1)
    if (ccw) ccw.classList.toggle('active', d === -1)
  }

  function isBoatVisible(bx, by, heading, fovVal) {
    var boatB = (Math.atan2(bx, by) * 180) / Math.PI
    /* Cone uses rotate(heading) inside worldG scale(S,-S); boresight world bearing = -heading in this atan2 convention. */
    var rel = (((boatB + heading + 540) % 360) - 180)
    return Math.abs(rel) <= fovVal / 2 && by > -0.05
  }

  function draw(p, bx, by, inFov) {
    if (!coneEl || SCALE === 0) return
    if (SCALE !== lastDrawScale) {
      lastDrawScale = SCALE
      updateScaleOnlySvgGeom()
    }
    updateTrackSvgGeomIfNeeded()
    syncConeAndPointerShape(p)
    dynamicCamG.setAttribute('transform', 'rotate(' + camHeading + ')')

    var segX = boatEnd.x - boatStart.x
    var segY = boatEnd.y - boatStart.y
    var udx = segX * boatDir
    var udy = segY * boatDir
    var pl = Math.hypot(segX, segY)
    /* Bow is drawn along +icon Y (world north). worldG uses scale(S,-S), so screen dir ∝ (udx,-udy). */
    var iconAngle = 0
    if (pl > 1e-5) {
      iconAngle = (Math.atan2(udy, udx) * 180) / Math.PI - 90
      lastTrailIconAngle = iconAngle
    } else if (!isNaN(lastTrailIconAngle)) iconAngle = lastTrailIconAngle
    boatIconG.setAttribute('transform', 'rotate(' + iconAngle + ')')

    if (bx !== lastDrawBx || by !== lastDrawBy) {
      lastDrawBx = bx
      lastDrawBy = by
      bearingLine.setAttribute('x2', bx)
      bearingLine.setAttribute('y2', by)
      boatG.setAttribute('transform', 'translate(' + bx + ',' + by + ')')
    }
    if (prevInFov !== inFov) {
      prevInFov = inFov
      boatHull.setAttribute('fill', inFov ? C.s : C.d)
      boatHull.setAttribute('stroke', inFov ? rgba(C.sr, 0.9) : rgba(C.dr, 0.85))
    }
    if (inFov) {
      boatHalo.setAttribute('display', '')
      boatHalo.setAttribute('fill', rgba(C.sr, 0.14))
    } else boatHalo.setAttribute('display', 'none')
  }

  function schedulePanelStats(p, bx, by, inFov) {
    panelStatsPayload = { p: p, bx: bx, by: by, inFov: inFov }
    if (!panelStatsRaf) panelStatsRaf = requestAnimationFrame(function () {
      panelStatsRaf = 0
      if (!panelStatsPayload) return
      var q = panelStatsPayload
      panelStatsPayload = null
      updateStats(q.p, q.bx, q.by, q.inFov)
    })
  }

  function updateStats(p, bx, by, inFov) {
    var c = statCache
    var dist = Math.hypot(bx, by)
    var st = p.frontArc / p.frontSpeed + (360 - p.frontArc) / p.backSpeed

    function u(el, k, s) {
      if (el && c[k] !== s) { el.textContent = s; c[k] = s }
    }

    u(c.elScan, 'lastScan', st.toFixed(1) + 's')
    u(c.elDist, 'lastDist', (dist * 1000).toFixed(0) + 'm')

    var travelM = (inFov ? detectedStreak : lastDetectedStreak).toFixed(1) + 'm'
    var blindM = (!inFov ? blindStreak : lastBlindStreak).toFixed(1) + 'm'
    if (c.elTravel) {
      u(c.elTravel, 'lastTravel', travelM)
      var to = inFov ? '1' : '0.5'
      if (c.lastTravelOp !== to) { c.elTravel.style.opacity = to; c.lastTravelOp = to }
    }
    if (c.elBlind) {
      u(c.elBlind, 'lastBlind', blindM)
      var bo = !inFov ? '1' : '0.5'
      if (c.lastBlindOp !== bo) { c.elBlind.style.opacity = bo; c.lastBlindOp = bo }
    }

    u(c.elTravelPrev, 'lastTravelPrev', prevDetectedStreak > 0 ? 'prev: ' + prevDetectedStreak.toFixed(1) + 'm' : 'prev: —')
    u(c.elBlindPrev, 'lastBlindPrev', prevBlindStreak > 0 ? 'prev: ' + prevBlindStreak.toFixed(1) + 'm' : 'prev: —')

    var prevTotalM = prevDetectedStreak + prevBlindStreak
    if (c.elRisk && c.elRiskBar) {
      if (prevTotalM >= MIN_BLIND_SHARE_M) {
        var share = (prevBlindStreak / prevTotalM) * 100
        var shareT = share.toFixed(0) + '%'
        var col = share > 66 ? 'var(--danger)' : share > 33 ? 'var(--warning)' : 'var(--success)'
        var w = share + '%'
        u(c.elRisk, 'lastRiskT', shareT)
        if (c.lastRiskCol !== col) { c.elRisk.style.color = col; c.lastRiskCol = col }
        if (c.lastRiskW !== w) { c.elRiskBar.style.width = w; c.lastRiskW = w }
        if (c.lastRiskBg !== col) { c.elRiskBar.style.background = col; c.lastRiskBg = col }
      } else {
        u(c.elRisk, 'lastRiskT', '—')
        if (c.lastRiskW !== '0%') { c.elRiskBar.style.width = '0%'; c.lastRiskW = '0%' }
      }
    }
    var vis = inFov ? 'YES' : 'NO'
    var visCls = 'val ' + (inFov ? 'active' : 'inactive')
    if (c.elVis) {
      u(c.elVis, 'lastVis', vis)
      if (c.lastVisCls !== visCls) { c.elVis.className = visCls; c.lastVisCls = visCls }
    }
  }

  function animate(ts) {
    if (!running || !svg) return
    if (lastTime === null) lastTime = ts
    var dt = Math.min((ts - lastTime) / 1000, 0.1)
    lastTime = ts
    var p = getParams()
    var boatKmS = p.boatSpeed * 0.000514
    var pathLen = Math.hypot(boatEnd.x - boatStart.x, boatEnd.y - boatStart.y)
    if (pathLen > 0.001) {
      boatT += boatDir * (boatKmS * dt) / pathLen
      if (boatT >= 1) { boatT = 1; boatDir = -1 }
      if (boatT <= 0) { boatT = 0; boatDir = 1 }
    }
    var speed = isFront(camHeading, p.frontArc) ? p.frontSpeed : p.backSpeed
    camHeading -= camDir * speed * dt
    if (camHeading >= 180) camHeading -= 360
    if (camHeading < -180) camHeading += 360
    var bx = boatStart.x + (boatEnd.x - boatStart.x) * boatT
    var by = boatStart.y + (boatEnd.y - boatStart.y) * boatT
    var visible = isBoatVisible(bx, by, camHeading, p.fov)
    var distThisFrame = p.boatSpeed * 0.514 * dt
    if (coneEl && SCALE > 0 && pathLen > 0.001 && !visible) appendTrail(bx, by)

    if (prevVisible !== null && visible !== prevVisible) {
      if (visible) {
        clearTrail(false)
        prevBlindStreak = blindStreak
        lastBlindStreak = blindStreak
        blindStreak = 0
      } else {
        prevDetectedStreak = detectedStreak
        lastDetectedStreak = detectedStreak
        detectedStreak = 0
      }
    }
    if (visible) detectedStreak += distThisFrame
    else blindStreak += distThisFrame
    prevVisible = visible

    if (!coneEl || SCALE === 0) updateStats(p, bx, by, visible)
    else {
      draw(p, bx, by, visible)
      schedulePanelStats(p, bx, by, visible)
    }
    if (running) requestAnimationFrame(animate)
  }

  function getCanvasXY(e) {
    var src = 'touches' in e && e.touches.length ? e.touches[0] : e
    return { x: (src.clientX - hitL) * hitSx, y: (src.clientY - hitT) * hitSy }
  }

  function onResize() {
    if (!resizeRaf) resizeRaf = requestAnimationFrame(function () { resizeRaf = 0; resize() })
  }

  function tryDragStart(e, thresh) {
    var pt = getCanvasXY(e)
    var s = worldToCanvas(boatStart.x, boatStart.y)
    var end = worldToCanvas(boatEnd.x, boatEnd.y)
    if (Math.hypot(pt.x - s.x, pt.y - s.y) < thresh) dragging = 'start'
    else if (Math.hypot(pt.x - end.x, pt.y - end.y) < thresh) dragging = 'end'
  }

  function dragToWorld(e) {
    var pt = getCanvasXY(e)
    var w = canvasToWorld(pt.x, pt.y)
    w.y = Math.max(0.05, Math.min(1.3, w.y))
    w.x = Math.max(-1.4, Math.min(1.4, w.x))
    if (dragging === 'start') boatStart = w
    else if (dragging === 'end') boatEnd = w
  }

  function onMouseDown(e) {
    lastPointerEv = e
    tryDragStart(e, 26)
    updateSvgCursor(e)
  }

  var CURSOR_NEAR = 30
  var lastPointerEv = null

  function updateSvgCursor(e) {
    if (!svg || !SCALE) return
    if (dragging) {
      svg.style.cursor = 'grabbing'
      return
    }
    var pt = getCanvasXY(e)
    var s = worldToCanvas(boatStart.x, boatStart.y)
    var end = worldToCanvas(boatEnd.x, boatEnd.y)
    if (Math.hypot(pt.x - s.x, pt.y - s.y) < CURSOR_NEAR ||
        Math.hypot(pt.x - end.x, pt.y - end.y) < CURSOR_NEAR)
      svg.style.cursor = 'grab'
    else svg.style.cursor = ''
  }

  function onMouseMove(e) {
    lastPointerEv = e
    if (dragging) dragToWorld(e)
    updateSvgCursor(e)
  }

  function onMouseUp() {
    dragging = null
    if (svg) {
      if (lastPointerEv) updateSvgCursor(lastPointerEv)
      else svg.style.cursor = ''
    }
  }

  function onTouchStart(e) {
    if (e.touches.length === 2) {
      lastPinchDist = Math.hypot(
        e.touches[0].clientX - e.touches[1].clientX,
        e.touches[0].clientY - e.touches[1].clientY)
      dragging = null
      return
    }
    if (e.touches.length !== 1) return
    e.preventDefault()
    tryDragStart(e, 34)
  }

  function onTouchMove(e) {
    if (e.touches.length === 2 && lastPinchDist !== null) {
      e.preventDefault()
      var dist = Math.hypot(
        e.touches[0].clientX - e.touches[1].clientX,
        e.touches[0].clientY - e.touches[1].clientY)
      applyZoom(dist - lastPinchDist)
      lastPinchDist = dist
      return
    }
    if (!dragging) return
    e.preventDefault()
    dragToWorld(e)
  }

  function onTouchEnd(e) {
    dragging = null
    if (e.touches.length < 2) lastPinchDist = null
  }

  function onWheel(e) {
    e.preventDefault()
    applyZoom(-e.deltaY)
  }

  function bindRange(id, valSpanId, onInput) {
    var input = $(id)
    var span = valSpanId ? $(valSpanId) : null
    function sync() { if (span) span.textContent = input.value }
    input.addEventListener('input', function () {
      sync()
      resetStreaks()
      if (onInput) onInput()
    })
    sync()
  }

  /** VOS #1 = shipped defaults; proposal #2 uses 50° FOV (slider is degrees, not a zoom %). */
  var CAMERA_PRESETS = {
    vos1:  { fov: 18, frontSpeed: 6, backSpeed: 60, frontArc: 180 },
    prop1: { fov: 18, frontSpeed: 7, backSpeed: 120, frontArc: 125 },
    prop2: { fov: 50, frontSpeed: 8, backSpeed: 120, frontArc: 125 },
  }

  function clearPresetDropdown() {
    var sel = $('camera-preset')
    if (sel) sel.value = ''
  }

  function applyCameraPreset(key) {
    var p = CAMERA_PRESETS[key]
    if (!p || !inpFov) return
    inpFov.value = String(p.fov)
    inpFrontSpeed.value = String(p.frontSpeed)
    inpBackSpeed.value = String(p.backSpeed)
    inpFrontArc.value = String(p.frontArc)
    $('val-fov').textContent = inpFov.value
    $('val-front-speed').textContent = inpFrontSpeed.value
    $('val-back-speed').textContent = inpBackSpeed.value
    $('val-front-arc').textContent = inpFrontArc.value
    cachedConeFov = cachedPtrLen = NaN
    resetStreaks()
    buildZones()
    var sel = $('camera-preset')
    if (sel) sel.value = key
  }

  function init() {
    svg = $('c')
    wrap = $('canvas-wrap')
    if (!svg || !wrap) return

    bgSky = svgEl('rect', { x: 0, y: 0, fill: 'var(--surface-1)' })
    bgSea = svgEl('rect', { x: 0, y: 0, fill: 'var(--surface-2)' })
    horizLine = svgEl('line', { x1: 0, 'stroke-dasharray': '6 4' })
    ringsG = svgEl('g', { id: 'rings' })
    compassG = svgEl('g', { id: 'compass' })
    zonesG = svgEl('g', { id: 'zones' })
    worldG = svgEl('g', { id: 'world' })
    worldG.appendChild(compassG)
    worldG.appendChild(zonesG)
    worldG.appendChild(ringsG)

    dynamicCamG = svgEl('g', { id: 'dynamic-cam' })
    coneEl = svgEl('path', { 'stroke-linejoin': 'round', 'stroke-width': 1, 'vector-effect': 'non-scaling-stroke' })
    camPointer = svgEl('line', { x1: 0, y1: 0, x2: 0, y2: 0.1, 'stroke-width': 1.5, 'vector-effect': 'non-scaling-stroke' })
    dynamicCamG.appendChild(coneEl)
    dynamicCamG.appendChild(camPointer)
    trajLine = svgEl('line', { 'stroke-width': 1, 'stroke-dasharray': '4 3', 'vector-effect': 'non-scaling-stroke' })
    boatTrail = svgEl('polyline', {
      fill: 'none', 'stroke-width': 2, 'stroke-linecap': 'round', 'stroke-linejoin': 'round',
      'vector-effect': 'non-scaling-stroke',
    })
    bearingLine = svgEl('line', { x1: 0, y1: 0, 'stroke-width': 0.5, 'vector-effect': 'non-scaling-stroke' })
    boatG = svgEl('g', { id: 'boat-layer' })
    boatHalo = svgEl('circle', { cx: 0, cy: 0, stroke: 'none' })
    boatIconG = svgEl('g')
    boatIconScaleG = svgEl('g')
    boatHull = svgEl('path', {
      d: 'M 0 1.05 L 0.38 0.22 L 0.26 -0.72 L -0.26 -0.72 L -0.38 0.22 Z',
      'stroke-width': 1.2, 'stroke-linejoin': 'round', 'vector-effect': 'non-scaling-stroke',
    })
    boatIconScaleG.appendChild(boatHull)
    boatIconG.appendChild(boatIconScaleG)
    boatG.appendChild(boatHalo)
    boatG.appendChild(boatIconG)
    anchorSOuter = svgEl('circle', {
      class: 'drag-anchor-ring drag-anchor-ring--start',
      fill: 'none', 'stroke-width': 2.5, 'vector-effect': 'non-scaling-stroke',
    })
    anchorS = svgEl('circle', { class: 'drag-anchor-core drag-anchor-core--start', 'stroke-width': 1.5, 'vector-effect': 'non-scaling-stroke' })
    anchorEOuter = svgEl('circle', {
      class: 'drag-anchor-ring drag-anchor-ring--end',
      fill: 'none', 'stroke-width': 2.5, 'vector-effect': 'non-scaling-stroke',
    })
    anchorE = svgEl('circle', { class: 'drag-anchor-core drag-anchor-core--end', 'stroke-width': 1.5, 'vector-effect': 'non-scaling-stroke' })
    anchorSLabel = svgEl('text', {
      class: 'drag-anchor-label',
      'text-anchor': 'middle', 'dominant-baseline': 'middle', transform: 'scale(1,-1)', 'font-family': FONT_SANS,
    })
    anchorSLabel.textContent = 'S'
    anchorELabel = svgEl('text', {
      class: 'drag-anchor-label drag-anchor-label--end',
      'text-anchor': 'middle', 'dominant-baseline': 'middle', transform: 'scale(1,-1)', 'font-family': FONT_SANS,
    })
    anchorELabel.textContent = 'E'
    camDot = svgEl('circle', { cx: 0, cy: 0, 'stroke-width': 1.5, 'vector-effect': 'non-scaling-stroke' })
    for (var ci = 0; ci < 4; ci++) camCorners.push(svgEl('line', { 'stroke-width': 1, 'vector-effect': 'non-scaling-stroke' }))

    worldG.appendChild(dynamicCamG)
    worldG.appendChild(trajLine)
    worldG.appendChild(boatTrail)
    worldG.appendChild(bearingLine)
    worldG.appendChild(boatG)
    worldG.appendChild(anchorSOuter)
    worldG.appendChild(anchorS)
    worldG.appendChild(anchorEOuter)
    worldG.appendChild(anchorE)
    worldG.appendChild(anchorSLabel)
    worldG.appendChild(anchorELabel)
    worldG.appendChild(camDot)
    for (var cj = 0; cj < 4; cj++) worldG.appendChild(camCorners[cj])

    svg.appendChild(bgSky)
    svg.appendChild(bgSea)
    svg.appendChild(horizLine)
    svg.appendChild(worldG)

    inpFov = $('input-fov')
    inpFrontSpeed = $('input-front-speed')
    inpBackSpeed = $('input-back-speed')
    inpFrontArc = $('input-front-arc')
    inpBoatSpeed = $('input-boat-speed')
    cachedConeFov = cachedConeR = cachedPtrLen = NaN
    lastDrawBx = lastDrawBy = NaN

    initTheme()
    running = true
    resize()
    updateZoomLabel()
    setDir(-1)
    window.addEventListener('resize', onResize)

    svg.addEventListener('mousedown', onMouseDown)
    svg.addEventListener('mousemove', onMouseMove)
    svg.addEventListener('mouseup', onMouseUp)
    svg.addEventListener('mouseleave', function () {
      if (!dragging) svg.style.cursor = ''
    })
    svg.addEventListener('touchstart', onTouchStart, { passive: false })
    svg.addEventListener('touchmove', onTouchMove, { passive: false })
    svg.addEventListener('touchend', onTouchEnd)
    svg.addEventListener('touchcancel', onTouchEnd)
    svg.addEventListener('wheel', onWheel, { passive: false })

    $('zoom-out').addEventListener('click', function () { applyZoom(-1) })
    $('zoom-in').addEventListener('click', function () { applyZoom(1) })
    $('dir-cw').addEventListener('click', function () { setDir(1) })
    $('dir-ccw').addEventListener('click', function () { setDir(-1) })
    bindRange('input-fov', 'val-fov', function () {
      cachedConeFov = cachedPtrLen = NaN
      clearPresetDropdown()
    })
    bindRange('input-front-speed', 'val-front-speed', clearPresetDropdown)
    bindRange('input-back-speed', 'val-back-speed', clearPresetDropdown)
    bindRange('input-front-arc', 'val-front-arc', function () {
      clearPresetDropdown()
      buildZones()
    })
    bindRange('input-boat-speed', 'val-boat-speed')

    var presetSelect = $('camera-preset')
    if (presetSelect) {
      presetSelect.addEventListener('change', function () {
        var k = presetSelect.value
        if (k) applyCameraPreset(k)
      })
    }

    statCache.elScan = $('st-scan')
    statCache.elDist = $('st-dist')
    statCache.elTravel = $('st-travel')
    statCache.elBlind = $('st-blind')
    statCache.elTravelPrev = $('st-travel-prev')
    statCache.elBlindPrev = $('st-blind-prev')
    statCache.elRisk = $('st-risk')
    statCache.elRiskBar = $('st-risk-bar')
    statCache.elVis = $('st-vis')

    requestAnimationFrame(animate)
  }

  if (document.readyState === 'loading') document.addEventListener('DOMContentLoaded', init)
  else init()
})()