'use strict';
/* ═══════════════════════════════════════════
   WavesSim v2  —  Волны и звук
   Modes: transverse | longitudinal | superposition | standing
   ─────────────────────────────────────────── */
class WavesSim {
  static BG   = '#0D0D1A';
  static FONT = "700 12px 'Manrope',sans-serif";
  static V    = '#9B5DE5';  /* violet  */
  static C    = '#06D6E0';  /* cyan    */
  static P    = '#F15BB5';  /* pink    */
  static G    = '#FFD166';  /* gold    */

  constructor(canvas) {
    this._c   = canvas;
    this._ctx = canvas.getContext('2d');
    this._dpr = 1;
    this._W   = 0;
    this._H   = 0;

    this._mode   = 'transverse';
    this._t      = 0;
    this._last   = null;
    this._raf    = null;
    this._paused = true;

    this._A1   = 50;  this._f1   = 1.0;  this._phi1 = 0;
    this._A2   = 40;  this._f2   = 1.5;  this._phi2 = 0;
    this._n    = 1;
    this._speed = 2.0;

    this._resizeObs = null;
    this.onUpdate   = null;
  }

  /* ── публичное API ── */

  fit() {
    const par = this._c.parentElement;
    const dpr = window.devicePixelRatio || 1;
    const w   = par.clientWidth  || 600;
    const h   = par.clientHeight || 400;
    this._c.width  = Math.round(w * dpr);
    this._c.height = Math.round(h * dpr);
    this._dpr = dpr;
    this._W   = w;
    this._H   = h;
    if (this._resizeObs) this._resizeObs.disconnect();
    this._resizeObs = new ResizeObserver(() => this.fit());
    this._resizeObs.observe(par);
    this.draw();
  }

  setMode(mode) {
    this._mode = mode;
    this._t    = 0;
    this._last = null;
    this.draw();
    this._emit();
  }

  getParams() {
    return { A1: this._A1, f1: this._f1, phi1: this._phi1, A2: this._A2, f2: this._f2, phi2: this._phi2,
             n: this._n, speed: this._speed, mode: this._mode };
  }
  setParams({ A1, f1, phi1, A2, f2, phi2, n, speed } = {}) {
    if (A1    !== undefined) this._A1    = Math.max(5,   Math.min(90, +A1));
    if (f1    !== undefined) this._f1    = Math.max(0.3, Math.min(4,  +f1));
    if (phi1  !== undefined) this._phi1  = +phi1;
    if (A2    !== undefined) this._A2    = Math.max(5,   Math.min(90, +A2));
    if (f2    !== undefined) this._f2    = Math.max(0.3, Math.min(4,  +f2));
    if (phi2  !== undefined) this._phi2  = +phi2;
    if (n     !== undefined) this._n     = Math.max(1, Math.min(5, Math.round(+n)));
    if (speed !== undefined) this._speed = Math.max(0.3, Math.min(5, +speed));
    this.draw();
    this._emit();
  }

  play() {
    this._paused = false;
    this._last   = null;
    if (!this._raf) this._raf = requestAnimationFrame(t => this._tick(t));
  }
  pause() {
    this._paused = true;
    if (this._raf) { cancelAnimationFrame(this._raf); this._raf = null; }
  }
  start() { this.play(); }
  stop()  { this.pause(); }
  reset() { this._t = 0; this._last = null; this.draw(); this._emit(); }

  info() {
    const v = (this._W || 600) / 3;
    return {
      T:      (1 / this._f1).toFixed(2),
      lambda: (v / this._f1).toFixed(0),
      v:      v.toFixed(0),
      f1:     this._f1
    };
  }

  /* ── анимационный цикл ── */

  _tick(ts) {
    if (!this._paused) {
      if (this._last !== null)
        this._t += Math.min((ts - this._last) / 1000, 0.05) * this._speed;
      this._last = ts;
      this._raf  = requestAnimationFrame(t => this._tick(t));
    } else {
      this._raf = null;
    }
    this.draw();
    this._emit();
  }

  /* ── главный draw ── */

  draw() {
    const { _ctx: ctx, _W: W, _H: H, _dpr: dpr } = this;
    if (!W || !H) return;
    /* сбрасываем трансформ + заливаем фон */
    ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
    ctx.fillStyle = WavesSim.BG;
    ctx.fillRect(0, 0, W, H);
    if      (this._mode === 'transverse')    this._transvDraw(ctx, W, H);
    else if (this._mode === 'longitudinal')  this._longDraw(ctx, W, H);
    else if (this._mode === 'superposition') this._superDraw(ctx, W, H);
    else                                     this._standDraw(ctx, W, H);
  }

  /* ══════════════════════════════════════
     ПОПЕРЕЧНАЯ ВОЛНА
  ══════════════════════════════════════ */
  _transvDraw(ctx, W, H) {
    const PL = 48, PR = 20, PT = 50, PB = 48;
    const cw = W - PL - PR;
    const ch = H - PT - PB;
    const cy = PT + ch / 2;

    this._grid(ctx, PL, PR, PT, PB, W, H);
    this._axisLine(ctx, PL, PR, PT, PB, W, H, cy);

    const A   = Math.max(4, Math.min(this._A1, ch / 2 - 8));
    const v   = cw / 3;
    const lam = v / this._f1;
    const k   = (2 * Math.PI) / lam;
    const om  = 2 * Math.PI * this._f1;
    const t   = this._t;
    const phi = this._phi1;
    const y   = x => A * Math.sin(om * t - k * (x - PL) + phi);

    /* волновая кривая */
    ctx.save();
    ctx.shadowColor = WavesSim.V;
    ctx.shadowBlur  = 16;
    ctx.strokeStyle = WavesSim.V;
    ctx.lineWidth   = 2.5;
    ctx.beginPath();
    for (let x = PL; x <= PL + cw; x += 1) {
      const py = cy + y(x);
      x === PL ? ctx.moveTo(x, py) : ctx.lineTo(x, py);
    }
    ctx.stroke();
    ctx.restore();

    /* частицы */
    const step = Math.max(12, Math.floor(lam / 10));
    for (let x = PL + step * 0.5; x < PL + cw; x += step) {
      const py   = cy + y(x);
      const norm = Math.abs(y(x)) / (A || 1);
      ctx.beginPath(); ctx.moveTo(x, cy); ctx.lineTo(x, py);
      ctx.strokeStyle = 'rgba(155,93,229,0.2)'; ctx.lineWidth = 1; ctx.stroke();
      ctx.save();
      ctx.shadowColor = WavesSim.V; ctx.shadowBlur = 8;
      ctx.beginPath(); ctx.arc(x, py, 4, 0, 6.28);
      ctx.fillStyle = `rgba(155,93,229,${(0.4 + 0.6 * norm).toFixed(2)})`; ctx.fill();
      ctx.restore();
    }

    /* выделенная частица */
    const hx = PL + Math.min(lam * 0.5, cw * 0.22);
    const hy = cy + y(hx);
    ctx.save();
    ctx.shadowColor = WavesSim.G; ctx.shadowBlur = 18;
    ctx.beginPath(); ctx.arc(hx, hy, 6, 0, 6.28);
    ctx.fillStyle = WavesSim.G; ctx.fill();
    ctx.restore();
    ctx.save();
    ctx.setLineDash([3, 4]);
    ctx.strokeStyle = 'rgba(255,209,102,0.22)'; ctx.lineWidth = 1;
    ctx.beginPath(); ctx.moveTo(hx, cy - A); ctx.lineTo(hx, cy + A); ctx.stroke();
    ctx.restore();

    /* аннотация длины волны */
    const ld = Math.min(lam, cw - 16);
    if (ld > 36) {
      const ay = cy + A + 26;
      ctx.save();
      ctx.strokeStyle = 'rgba(6,214,224,0.7)'; ctx.lineWidth = 1.4;
      ctx.beginPath();
      ctx.moveTo(PL + 8, ay); ctx.lineTo(PL + 8 + ld, ay);
      ctx.moveTo(PL + 13, ay - 4); ctx.lineTo(PL + 8, ay); ctx.lineTo(PL + 13, ay + 4);
      ctx.moveTo(PL + 8 + ld - 5, ay - 4); ctx.lineTo(PL + 8 + ld, ay); ctx.lineTo(PL + 8 + ld - 5, ay + 4);
      ctx.stroke();
      ctx.fillStyle = WavesSim.C; ctx.textAlign = 'center';
      ctx.font = "700 10px 'Manrope',sans-serif";
      ctx.fillText('\u03bb = ' + ld.toFixed(0), PL + 8 + ld / 2, ay - 5);
      ctx.restore();
    }

    /* аннотация амплитуды */
    if (A > 16) {
      const ax = PL - 20;
      ctx.save();
      ctx.strokeStyle = 'rgba(241,91,181,0.7)'; ctx.lineWidth = 1.4;
      ctx.beginPath();
      ctx.moveTo(ax, cy); ctx.lineTo(ax, cy - A);
      ctx.moveTo(ax - 4, cy - A + 5); ctx.lineTo(ax, cy - A); ctx.lineTo(ax + 4, cy - A + 5);
      ctx.moveTo(ax - 3, cy - 3);     ctx.lineTo(ax, cy);     ctx.lineTo(ax + 3, cy - 3);
      ctx.stroke();
      ctx.fillStyle = WavesSim.P; ctx.textAlign = 'center';
      ctx.font = "700 10px 'Manrope',sans-serif";
      ctx.save(); ctx.translate(ax - 12, cy - A / 2); ctx.rotate(-Math.PI / 2);
      ctx.fillText('A', 0, 0); ctx.restore();
      ctx.restore();
    }

    /* подпись */
    ctx.fillStyle = 'rgba(255,255,255,0.28)';
    ctx.font = WavesSim.FONT; ctx.textAlign = 'left';
    ctx.fillText('y = A sin(\u03c9t \u2212 kx + \u03c6)', PL, PT - 14);
  }

  /* ══════════════════════════════════════
     ПРОДОЛЬНАЯ ВОЛНА
  ══════════════════════════════════════ */
  _longDraw(ctx, W, H) {
    const PL = 24, PR = 24, PT = 50, PB = 60;
    const cw = W - PL - PR;
    const ch = H - PT - PB;

    const nRows = 5;
    const rowH  = ch / nRows;
    const nPart = Math.max(20, Math.floor(cw / 10));
    const dx0   = cw / nPart;

    const v   = cw / 3;
    const lam = v / this._f1;
    const k   = (2 * Math.PI) / lam;
    const om  = 2 * Math.PI * this._f1;
    const A   = Math.min(this._A1 * 0.5, lam / 4, rowH * 0.36);
    const t   = this._t;
    const phi = this._phi1;

    /* ряды частиц */
    for (let row = 0; row < nRows; row++) {
      const cy = PT + rowH * (row + 0.5);
      for (let i = 0; i < nPart; i++) {
        const x0    = PL + (i + 0.5) * dx0;
        const phase = om * t - k * (x0 - PL) + phi;
        const disp  = A * Math.sin(phase);
        const xd    = Math.max(PL + 1, Math.min(PL + cw - 1, x0 + disp));
        const dens  = 1 / Math.max(0.15, 1 + (-A * k * Math.cos(phase)));
        const alpha = Math.max(0.1, Math.min(0.95, dens * 0.55));
        ctx.beginPath(); ctx.arc(xd, cy, 3, 0, 6.28);
        ctx.fillStyle = `rgba(155,93,229,${alpha.toFixed(2)})`; ctx.fill();
      }
    }

    /* график давления */
    const pTop = PT + ch + 10;
    const pH   = H - pTop - 8;
    if (pH > 20) {
      const axY = pTop + pH / 2;
      ctx.strokeStyle = 'rgba(255,255,255,0.08)'; ctx.lineWidth = 1;
      ctx.setLineDash([4, 3]);
      ctx.beginPath(); ctx.moveTo(PL, axY); ctx.lineTo(PL + cw, axY); ctx.stroke();
      ctx.setLineDash([]);
      ctx.save();
      ctx.shadowColor = WavesSim.C; ctx.shadowBlur = 8;
      ctx.strokeStyle = WavesSim.C; ctx.lineWidth = 2;
      ctx.beginPath();
      for (let x = PL; x <= PL + cw; x += 1) {
        const py = axY - Math.cos(om * t - k * (x - PL) + phi) * pH * 0.4;
        x === PL ? ctx.moveTo(x, py) : ctx.lineTo(x, py);
      }
      ctx.stroke(); ctx.restore();
      ctx.fillStyle = WavesSim.C; ctx.font = "600 9px 'Manrope',sans-serif"; ctx.textAlign = 'left';
      ctx.fillText('P(x,t)', PL + 2, pTop + 11);
    }

    ctx.fillStyle = 'rgba(255,255,255,0.28)';
    ctx.font = WavesSim.FONT; ctx.textAlign = 'left';
    ctx.fillText('Продольная волна', PL, PT - 16);
  }

  /* ══════════════════════════════════════
     СУПЕРПОЗИЦИЯ
  ══════════════════════════════════════ */
  _superDraw(ctx, W, H) {
    const PL = 48, PR = 20, PT = 70, PB = 48;
    const cw = W - PL - PR;
    const ch = H - PT - PB;
    const cy = PT + ch / 2;

    this._grid(ctx, PL, PR, PT, PB, W, H);
    this._axisLine(ctx, PL, PR, PT, PB, W, H, cy);

    const v  = cw / 3;
    const t  = this._t;

    const mk = (f, A) => {
      const lam = v / f, k = (2 * Math.PI) / lam, om = 2 * Math.PI * f;
      const amp = Math.max(4, Math.min(A, ch / 2 - 8));
      return { k, om, amp };
    };

    const w1  = mk(this._f1, this._A1);
    const w2  = mk(this._f2, this._A2);
    const y1  = x => w1.amp * Math.sin(w1.om * t - w1.k * (x - PL) + this._phi1);
    const y2  = x => w2.amp * Math.sin(w2.om * t - w2.k * (x - PL) + this._phi2);
    const yR  = x => y1(x) + y2(x);

    this._waveLine(ctx, PL, cw, cy, y1, WavesSim.V, 1.5, 0.45, false);
    this._waveLine(ctx, PL, cw, cy, y2, WavesSim.C, 1.5, 0.45, false);
    this._waveLine(ctx, PL, cw, cy, yR, WavesSim.P, 2.8, 1.0,  true);

    /* легенда */
    const items = [
      { c: WavesSim.V, txt: 'y\u2081 = A\u2081 sin(\u03c9\u2081t \u2212 k\u2081x + \u03c6\u2081)' },
      { c: WavesSim.C, txt: 'y\u2082 = A\u2082 sin(\u03c9\u2082t \u2212 k\u2082x + \u03c6\u2082)' },
      { c: WavesSim.P, txt: 'y = y\u2081 + y\u2082' },
    ];
    ctx.font = "600 9px 'Manrope',sans-serif";
    items.forEach((it, i) => {
      const lx = PL + 6, ly = PT - 56 + i * 18;
      ctx.save();
      ctx.shadowColor = it.c; ctx.shadowBlur = 8;
      ctx.fillStyle = it.c;
      ctx.beginPath(); ctx.arc(lx + 4, ly + 4, 3.5, 0, 6.28); ctx.fill();
      ctx.restore();
      ctx.fillStyle = 'rgba(255,255,255,0.55)'; ctx.textAlign = 'left';
      ctx.fillText(it.txt, lx + 13, ly + 8);
    });
  }

  /* ══════════════════════════════════════
     СТОЯЧАЯ ВОЛНА
  ══════════════════════════════════════ */
  _standDraw(ctx, W, H) {
    const PL = 48, PR = 20, PT = 50, PB = 48;
    const cw = W - PL - PR;
    const ch = H - PT - PB;
    const cy = PT + ch / 2;

    this._grid(ctx, PL, PR, PT, PB, W, H);
    this._axisLine(ctx, PL, PR, PT, PB, W, H, cy);

    const n   = this._n;
    const k   = (n * Math.PI) / cw;
    const om  = 2 * Math.PI * this._f1;
    const A   = Math.max(4, Math.min(this._A1, ch / 2 - 10));
    const t   = this._t;

    /* прямая и обратная (тусклые) */
    this._waveLine(ctx, PL, cw, cy, x =>  A * Math.sin(om * t - k * (x - PL)),         WavesSim.V, 1.0, 0.25, false);
    this._waveLine(ctx, PL, cw, cy, x =>  A * Math.sin(om * t + k * (x - PL) + Math.PI), WavesSim.C, 1.0, 0.25, false);

    /* огибающая */
    ctx.save();
    ctx.globalAlpha = 0.12;
    ctx.fillStyle = WavesSim.V;
    ctx.beginPath(); ctx.moveTo(PL, cy);
    for (let x = PL; x <= PL + cw; x++) ctx.lineTo(x, cy - 2 * A * Math.abs(Math.sin(k * (x - PL))));
    for (let x = PL + cw; x >= PL; x--) ctx.lineTo(x, cy + 2 * A * Math.abs(Math.sin(k * (x - PL))));
    ctx.closePath(); ctx.fill(); ctx.restore();

    /* стоячая волна */
    const cosT = Math.cos(om * t + this._phi1);
    this._waveLine(ctx, PL, cw, cy, x => 2 * A * Math.sin(k * (x - PL)) * cosT, WavesSim.G, 2.8, 1.0, true);

    /* узлы (cyan) */
    ctx.save(); ctx.shadowColor = WavesSim.C; ctx.shadowBlur = 10; ctx.fillStyle = WavesSim.C;
    for (let m = 0; m <= n; m++) {
      ctx.beginPath(); ctx.arc(PL + m * cw / n, cy, 5, 0, 6.28); ctx.fill();
    }
    ctx.restore();

    /* пучности (pink) */
    ctx.save(); ctx.shadowColor = WavesSim.P; ctx.shadowBlur = 12; ctx.fillStyle = WavesSim.P;
    for (let m = 0; m < n; m++) {
      const ax = PL + (m + 0.5) * cw / n;
      const ay = cy + 2 * A * Math.sin(k * (ax - PL)) * cosT;
      ctx.beginPath(); ctx.arc(ax, ay, 5, 0, 6.28); ctx.fill();
    }
    ctx.restore();

    /* легенда */
    const lx = W - PR - 128, ly = PT - 20;
    ctx.font = "600 9px 'Manrope',sans-serif";
    [{ c: WavesSim.C, t: 'Узел (y\u22610)', dy: 0 }, { c: WavesSim.P, t: 'Пучность', dy: 16 }].forEach(r => {
      ctx.save(); ctx.shadowColor = r.c; ctx.shadowBlur = 8; ctx.fillStyle = r.c;
      ctx.beginPath(); ctx.arc(lx + 5, ly + r.dy + 5, 4, 0, 6.28); ctx.fill(); ctx.restore();
      ctx.fillStyle = 'rgba(255,255,255,0.5)'; ctx.textAlign = 'left';
      ctx.fillText(r.t, lx + 14, ly + r.dy + 9);
    });

    ctx.fillStyle = 'rgba(255,255,255,0.28)'; ctx.font = WavesSim.FONT; ctx.textAlign = 'left';
    ctx.fillText('n = ' + n + '   \u03bb = 2L/' + n, PL, PT - 14);
  }

  /* ══════════════════════════════════════
     ВСПОМОГАТЕЛЬНЫЕ
  ══════════════════════════════════════ */

  _waveLine(ctx, PL, cw, cy, fn, color, lw, alpha, glow) {
    ctx.save();
    ctx.globalAlpha = alpha;
    if (glow) { ctx.shadowColor = color; ctx.shadowBlur = 16; }
    ctx.strokeStyle = color; ctx.lineWidth = lw;
    ctx.beginPath();
    for (let x = PL; x <= PL + cw; x += 1) {
      const py = cy + fn(x);
      x === PL ? ctx.moveTo(x, py) : ctx.lineTo(x, py);
    }
    ctx.stroke(); ctx.restore();
  }

  _grid(ctx, PL, PR, PT, PB, W, H) {
    ctx.strokeStyle = 'rgba(255,255,255,0.04)'; ctx.lineWidth = 1;
    ctx.beginPath();
    for (let y = PT; y <= H - PB; y += 28) { ctx.moveTo(PL, y); ctx.lineTo(W - PR, y); }
    for (let x = PL; x <= W - PR; x += 40) { ctx.moveTo(x, PT); ctx.lineTo(x, H - PB); }
    ctx.stroke();
  }

  _axisLine(ctx, PL, PR, PT, PB, W, H, cy) {
    ctx.save();
    ctx.setLineDash([6, 4]);
    ctx.strokeStyle = 'rgba(255,255,255,0.12)'; ctx.lineWidth = 1;
    ctx.beginPath(); ctx.moveTo(PL, cy); ctx.lineTo(W - PR, cy); ctx.stroke();
    ctx.restore();
    ctx.strokeStyle = 'rgba(255,255,255,0.18)'; ctx.lineWidth = 1;
    ctx.beginPath();
    ctx.moveTo(PL, PT - 6); ctx.lineTo(PL, H - PB);
    ctx.moveTo(PL, H - PB); ctx.lineTo(W - PR + 6, H - PB);
    ctx.stroke();
    ctx.fillStyle = 'rgba(255,255,255,0.22)';
    ctx.font = "600 9px 'Manrope',sans-serif";
    ctx.textAlign = 'right';  ctx.fillText('y', PL - 4, PT);
    ctx.textAlign = 'left';   ctx.fillText('x', W - PR + 8, H - PB + 4);
  }

  _emit() { if (this.onUpdate) this.onUpdate(this.info()); }
}

/* ─── lab UI init ─────────────────────────────────── */
  function _openWaves() {
    document.getElementById('sim-topbar-title').textContent = 'Волны и звук';
    document.getElementById('ctrl-waves').style.display = '';
    _simShow('sim-waves');
    _registerSimState('waves', () => wavesSim?.getParams(),
      st => { if (wavesSim) { if (st.mode) wavesSim.setMode(st.mode); wavesSim.setParams(st); } });
    if (_embedMode) _startStateEmit('waves');
    requestAnimationFrame(() => requestAnimationFrame(() => {
      if (!wavesSim) {
        wavesSim = new WavesSim(document.getElementById('waves-canvas'));
        wavesSim.onUpdate = _wavesUpdateUI;
      }
      wavesSim.fit();
      wavesSim.reset();
      wavesSim.play();
      _wavesUpdateUI(wavesSim.info());
    }));
  }

  function wavesMode(mode, btn) {
    document.querySelectorAll('.wave-mode-btn').forEach(b => b.classList.remove('active'));
    if (btn) btn.classList.add('active');
    document.getElementById('waves-w2-section').style.display = mode === 'superposition' ? '' : 'none';
    document.getElementById('waves-n-section').style.display  = mode === 'standing'      ? '' : 'none';
    if (wavesSim) wavesSim.setMode(mode);
  }

  function wavesParam(name, val) {
    const v = parseFloat(val);
    const el = (id, txt) => { const e = document.getElementById(id); if (e) e.textContent = txt; };
    if (name === 'A1')    el('waves-A1-val',    v);
    if (name === 'f1')    el('waves-f1-val',    v.toFixed(1) + ' Гц');
    if (name === 'phi1')  el('waves-phi1-val',  v.toFixed(1));
    if (name === 'A2')    el('waves-A2-val',    v);
    if (name === 'f2')    el('waves-f2-val',    v.toFixed(1) + ' Гц');
    if (name === 'phi2')  el('waves-phi2-val',  v.toFixed(1));
    if (name === 'speed') el('waves-speed-val', '\u00d7' + v.toFixed(1));
    if (wavesSim) wavesSim.setParams({ [name]: v });
  }

  function wavesN(n, btn) {
    document.querySelectorAll('.wave-n-btn').forEach(b => b.classList.remove('active'));
    if (btn) btn.classList.add('active');
    if (wavesSim) wavesSim.setParams({ n });
  }

  function wavesPreset(name) {
    const presets = {
      constructive: { A1: 50, f1: 1.0, phi1: 0, A2: 50, f2: 1.0, phi2: 0 },
      destructive:  { A1: 50, f1: 1.0, phi1: 0, A2: 50, f2: 1.0, phi2: 3.14 },
      beats:        { A1: 50, f1: 1.0, phi1: 0, A2: 50, f2: 1.3, phi2: 0 },
    };
    const p = presets[name]; if (!p) return;
    document.getElementById('sl-waves-A1').value   = p.A1;
    document.getElementById('sl-waves-f1').value   = p.f1;
    document.getElementById('sl-waves-phi1').value = p.phi1;
    document.getElementById('sl-waves-A2').value   = p.A2;
    document.getElementById('sl-waves-f2').value   = p.f2;
    document.getElementById('sl-waves-phi2').value = p.phi2;
    document.getElementById('waves-A1-val').textContent   = p.A1;
    document.getElementById('waves-f1-val').textContent   = p.f1.toFixed(1) + ' Гц';
    document.getElementById('waves-phi1-val').textContent = p.phi1.toFixed(1);
    document.getElementById('waves-A2-val').textContent   = p.A2;
    document.getElementById('waves-f2-val').textContent   = p.f2.toFixed(1) + ' Гц';
    document.getElementById('waves-phi2-val').textContent = p.phi2.toFixed(1);
    if (wavesSim) wavesSim.setParams({ A1: p.A1, f1: p.f1, phi1: p.phi1, A2: p.A2, f2: p.f2, phi2: p.phi2 });
  }

  function wavesPlayPause() {
    if (!wavesSim) return;
    const btn = document.getElementById('waves-play-btn');
    if (wavesSim._paused) {
      wavesSim.play();
      btn.innerHTML = '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.2"><rect x="6" y="4" width="4" height="16"/><rect x="14" y="4" width="4" height="16"/></svg>';
    } else {
      wavesSim.pause();
      btn.innerHTML = '<svg viewBox="0 0 24 24" fill="currentColor"><polygon points="5 3 19 12 5 21 5 3"/></svg>';
    }
  }

  function _wavesUpdateUI(info) {
    const v = (id, val) => { const e = document.getElementById(id); if (e) e.textContent = val; };
    v('wavesbar-T',   info.T);
    v('wavesbar-lam', info.lambda);
    v('wavesbar-v',   info.v);
    v('wavesbar-f',   (+info.f1).toFixed(1));
  }

  /* ── crystal lattice (3D) ── */
