const pptxgen = require("pptxgenjs");
const pres = new pptxgen();
pres.layout = "LAYOUT_WIDE"; // 13.3 x 7.5 inches - more space for flowcharts

// ─── COLOR PALETTE ───────────────────────────────────────────────────────────
const C = {
  darkBg:   "0D1B2A",   // deep navy - title slides
  midBg:    "1B2F4B",   // medium navy
  accent1:  "2196F3",   // vivid blue - main boxes
  accent2:  "00BCD4",   // cyan - sub-boxes
  accent3:  "FF9800",   // amber - outcomes / results
  accent4:  "4CAF50",   // green - positive effects
  accent5:  "F44336",   // red - negative effects
  accentPu: "9C27B0",   // purple - special nodes
  lightBg:  "EBF5FB",   // very light blue background
  white:    "FFFFFF",
  textDark: "1A237E",   // deep blue text
  textMid:  "263238",
  gray:     "B0BEC5",
  arrowClr: "37474F",
};

// ─── HELPERS ─────────────────────────────────────────────────────────────────

function addSlideTitle(slide, title, subtitle) {
  slide.background = { color: C.darkBg };
  slide.addShape("rect", { x: 0, y: 0, w: 13.3, h: 7.5, fill: { color: C.darkBg } });
  // decorative bar
  slide.addShape("rect", { x: 0, y: 6.8, w: 13.3, h: 0.7, fill: { color: C.accent1 } });
  slide.addText(title, {
    x: 0.5, y: 2.2, w: 12.3, h: 1.2,
    fontSize: 44, bold: true, color: C.white, align: "center", fontFace: "Calibri"
  });
  if (subtitle) {
    slide.addText(subtitle, {
      x: 0.5, y: 3.7, w: 12.3, h: 0.7,
      fontSize: 22, color: C.accent2, align: "center", fontFace: "Calibri", italic: true
    });
  }
  slide.addText("Ref: Sembulingam — Essentials of Medical Physiology", {
    x: 0.5, y: 6.85, w: 12.3, h: 0.5,
    fontSize: 13, color: C.white, align: "center", fontFace: "Calibri"
  });
}

// Draw a box with centered text, returns nothing (adds to slide directly)
function box(slide, label, x, y, w, h, fillColor, textColor, fontSize, bold) {
  slide.addShape("roundRect", {
    x, y, w, h,
    fill: { color: fillColor || C.accent1 },
    line: { color: C.white, width: 1.5 },
    rectRadius: 0.12
  });
  slide.addText(label, {
    x, y, w, h,
    fontSize: fontSize || 12, bold: bold !== false, color: textColor || C.white,
    align: "center", valign: "middle", fontFace: "Calibri", wrap: true, margin: 4
  });
}

// Draw a diamond shape
function diamond(slide, label, x, y, w, h, fillColor, textColor, fontSize) {
  slide.addShape("diamond", {
    x, y, w, h,
    fill: { color: fillColor || C.accent3 },
    line: { color: C.white, width: 1.5 }
  });
  slide.addText(label, {
    x, y, w, h,
    fontSize: fontSize || 11, bold: true, color: textColor || C.textDark,
    align: "center", valign: "middle", fontFace: "Calibri", wrap: true, margin: 5
  });
}

// Vertical arrow
function arrowDown(slide, x, y, len, label) {
  slide.addShape("line", {
    x, y, w: 0, h: len,
    line: { color: C.arrowClr, width: 2.0, endArrowType: "triangle" }
  });
  if (label) {
    slide.addText(label, {
      x: x + 0.05, y: y + len / 2 - 0.15, w: 1.2, h: 0.3,
      fontSize: 9, color: C.arrowClr, fontFace: "Calibri"
    });
  }
}

// Horizontal arrow right
function arrowRight(slide, x, y, len, label) {
  slide.addShape("line", {
    x, y, w: len, h: 0,
    line: { color: C.arrowClr, width: 2.0, endArrowType: "triangle" }
  });
  if (label) {
    slide.addText(label, {
      x: x + len / 2 - 0.3, y: y - 0.25, w: 1.0, h: 0.3,
      fontSize: 9, color: C.arrowClr, fontFace: "Calibri", align: "center"
    });
  }
}

// Horizontal arrow left
function arrowLeft(slide, x, y, len, label) {
  slide.addShape("line", {
    x, y, w: -len, h: 0,
    line: { color: C.arrowClr, width: 2.0, endArrowType: "triangle" }
  });
}

function arrowUp(slide, x, y, len) {
  slide.addShape("line", {
    x, y, w: 0, h: -len,
    line: { color: C.arrowClr, width: 2.0, endArrowType: "triangle" }
  });
}

function sectionHeader(slide, text, color) {
  slide.addShape("rect", { x: 0, y: 0, w: 13.3, h: 0.6, fill: { color: color || C.midBg } });
  slide.addText(text, {
    x: 0.2, y: 0, w: 12.9, h: 0.6,
    fontSize: 18, bold: true, color: C.white, align: "center", valign: "middle", fontFace: "Calibri"
  });
}

// ═══════════════════════════════════════════════════════════════════════════════
// SLIDE 1 — TITLE SLIDE
// ═══════════════════════════════════════════════════════════════════════════════
{
  const sl = pres.addSlide();
  addSlideTitle(sl, "HEART RATE", "Full Chapter Flowcharts — Essentials of Medical Physiology (Sembulingam)");
  // decorative heart symbol area
  sl.addText("❤", { x: 5.9, y: 1.0, w: 1.5, h: 1.0, fontSize: 52, color: C.accent5, align: "center" });
}

// ═══════════════════════════════════════════════════════════════════════════════
// SLIDE 2 — OVERVIEW / DEFINITION OF HEART RATE
// ═══════════════════════════════════════════════════════════════════════════════
{
  const sl = pres.addSlide();
  sl.background = { color: C.lightBg };
  sectionHeader(sl, "HEART RATE — DEFINITION & NORMAL VALUES", C.midBg);

  // Central topic box
  box(sl, "HEART RATE", 5.15, 0.75, 3.0, 0.7, C.accent1, C.white, 18, true);
  arrowDown(sl, 6.65, 1.45, 0.45);

  // Definition
  box(sl, "Number of times the heart beats per minute (beats/min)", 4.15, 1.9, 5.0, 0.75, C.midBg, C.white, 13);
  arrowDown(sl, 6.65, 2.65, 0.4);

  // Normal value box
  box(sl, "Normal Heart Rate\n60 – 100 beats/min", 5.0, 3.05, 3.3, 0.8, C.accent3, C.textDark, 13);
  arrowDown(sl, 6.65, 3.85, 0.35);

  // Three branches from normal HR
  // Left arrow
  sl.addShape("line", { x: 6.65, y: 4.2, w: -3.4, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  // Right arrow
  sl.addShape("line", { x: 6.65, y: 4.2, w: 3.4, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  // Center down arrow
  arrowDown(sl, 6.65, 4.2, 0.4);

  // Bradycardia
  sl.addShape("line", { x: 3.25, y: 4.2, w: 0, h: 0.4, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  box(sl, "BRADYCARDIA\n< 60 beats/min\n(Slow heart rate)", 1.9, 4.6, 2.7, 1.0, C.accentPu, C.white, 12);

  // Normal
  sl.addShape("line", { x: 6.65, y: 4.2, w: 0, h: 0.4, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  box(sl, "NORMAL\n60 – 100 beats/min\n(Healthy adult at rest)", 5.1, 4.6, 3.1, 1.0, C.accent4, C.white, 12);

  // Tachycardia
  sl.addShape("line", { x: 10.05, y: 4.2, w: 0, h: 0.4, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  box(sl, "TACHYCARDIA\n> 100 beats/min\n(Fast heart rate)", 8.65, 4.6, 2.7, 1.0, C.accent5, C.white, 12);

  arrowDown(sl, 6.65, 5.6, 0.35);

  // Bottom note: Newborn vs adult
  box(sl, "Newborn: ~120 beats/min   |   Child (5 yrs): ~90 beats/min   |   Adult: 72 beats/min (average)", 1.5, 5.95, 10.3, 0.65, C.accent2, C.textDark, 12);
}

// ═══════════════════════════════════════════════════════════════════════════════
// SLIDE 3 — SA NODE AS PACEMAKER (Origin of Heart Rate)
// ═══════════════════════════════════════════════════════════════════════════════
{
  const sl = pres.addSlide();
  sl.background = { color: C.lightBg };
  sectionHeader(sl, "ORIGIN OF HEART RATE — SA NODE (PACEMAKER)", C.midBg);

  // SA Node top box
  box(sl, "SA NODE\n(Sinoatrial Node)", 5.15, 0.75, 3.0, 0.75, C.accent1, C.white, 14);
  arrowDown(sl, 6.65, 1.5, 0.35);

  box(sl, "Located at junction of right atrium and superior vena cava", 4.4, 1.85, 4.5, 0.65, C.midBg, C.white, 12);
  arrowDown(sl, 6.65, 2.5, 0.35);

  box(sl, "PACEMAKER POTENTIAL (Automatic / Self-Excitation)", 4.3, 2.85, 4.7, 0.65, C.accent3, C.textDark, 13);
  arrowDown(sl, 6.65, 3.5, 0.35);

  // Three properties
  sl.addShape("line", { x: 6.65, y: 3.85, w: -3.5, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 6.65, y: 3.85, w: 3.5, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  arrowDown(sl, 6.65, 3.85, 0.3);

  sl.addShape("line", { x: 3.15, y: 3.85, w: 0, h: 0.3, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  box(sl, "AUTOMATICITY\nSpontaneous firing\nwithout nerve stimulation", 1.5, 4.15, 3.3, 0.95, C.accent2, C.textDark, 11);

  sl.addShape("line", { x: 6.65, y: 3.85, w: 0, h: 0.3, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  box(sl, "RHYTHMICITY\nRegular, repetitive\nfiring pattern", 4.9, 4.15, 3.5, 0.95, C.accent4, C.textDark, 11);

  sl.addShape("line", { x: 10.15, y: 3.85, w: 0, h: 0.3, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  box(sl, "CONDUCTIVITY\nSpreads impulse to\nentire heart", 8.5, 4.15, 3.3, 0.95, C.accentPu, C.white, 11);

  arrowDown(sl, 6.65, 5.1, 0.35);

  // Impulse conduction path
  box(sl, "Impulse from SA Node   →   AV Node   →   Bundle of His   →   Purkinje Fibers   →   Ventricles Contract", 1.0, 5.45, 11.3, 0.7, C.accent1, C.white, 12);
  arrowDown(sl, 6.65, 6.15, 0.35);

  box(sl, "One complete HEART BEAT = Atrial contraction + Ventricular contraction", 3.5, 6.5, 6.3, 0.65, C.accent3, C.textDark, 12);
}

// ═══════════════════════════════════════════════════════════════════════════════
// SLIDE 4 — FACTORS AFFECTING HEART RATE (Overview)
// ═══════════════════════════════════════════════════════════════════════════════
{
  const sl = pres.addSlide();
  sl.background = { color: C.lightBg };
  sectionHeader(sl, "FACTORS AFFECTING HEART RATE — OVERVIEW", C.midBg);

  // Central box
  box(sl, "HEART RATE\nREGULATION", 5.3, 0.75, 2.7, 0.9, C.accent1, C.white, 14);

  // 6 branches radiating out
  const factors = [
    { label: "1. NERVOUS\nSystem", x: 0.3, y: 1.05, color: C.midBg },
    { label: "2. CHEMICAL\nFactors", x: 0.3, y: 2.4, color: C.accent2 },
    { label: "3. HORMONES", x: 0.3, y: 3.75, color: C.accentPu },
    { label: "4. TEMPERATURE", x: 9.8, y: 1.05, color: C.accent3 },
    { label: "5. EXERCISE &\nPhysical", x: 9.8, y: 2.4, color: C.accent4 },
    { label: "6. AGE, SEX &\nOther Factors", x: 9.8, y: 3.75, color: C.accent5 },
  ];

  factors.forEach((f, i) => {
    box(sl, f.label, f.x, f.y, 2.7, 0.75, f.color, C.white, 12);
    if (i < 3) {
      sl.addShape("line", { x: 3.0, y: f.y + 0.37, w: 2.3, h: 0, line: { color: C.arrowClr, width: 1.6, endArrowType: "triangle" } });
    } else {
      sl.addShape("line", { x: 9.8, y: f.y + 0.37, w: -2.3, h: 0, line: { color: C.arrowClr, width: 1.6, endArrowType: "triangle" } });
    }
  });

  arrowDown(sl, 6.65, 1.65, 0.4);

  // Bottom section - key message
  box(sl, "All these factors either INCREASE or DECREASE heart rate by acting on the SA node (pacemaker)", 1.5, 4.8, 10.3, 0.7, C.midBg, C.white, 13);
  arrowDown(sl, 6.65, 5.5, 0.35);

  // Two outcomes
  sl.addShape("line", { x: 6.65, y: 5.85, w: -2.8, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 6.65, y: 5.85, w: 2.8, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 3.85, y: 5.85, w: 0, h: 0.35, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  sl.addShape("line", { x: 9.45, y: 5.85, w: 0, h: 0.35, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  box(sl, "↑ TACHYCARDIA\n(Heart rate increases)", 2.35, 6.2, 3.0, 0.8, C.accent5, C.white, 12);
  box(sl, "↓ BRADYCARDIA\n(Heart rate decreases)", 8.0, 6.2, 3.0, 0.8, C.accentPu, C.white, 12);
}

// ═══════════════════════════════════════════════════════════════════════════════
// SLIDE 5 — NERVOUS SYSTEM REGULATION (SYMPATHETIC)
// ═══════════════════════════════════════════════════════════════════════════════
{
  const sl = pres.addSlide();
  sl.background = { color: C.lightBg };
  sectionHeader(sl, "NERVOUS REGULATION — SYMPATHETIC SYSTEM (Increases Heart Rate)", C.accent5);

  box(sl, "SYMPATHETIC NERVOUS SYSTEM\n(Cardioaccelerator Nerves)", 4.3, 0.75, 4.7, 0.8, C.accent5, C.white, 14);
  arrowDown(sl, 6.65, 1.55, 0.4);

  box(sl, "Originates in Cardioaccelerator Center (CAC)\nin Medulla Oblongata", 4.3, 1.95, 4.7, 0.75, C.midBg, C.white, 12);
  arrowDown(sl, 6.65, 2.7, 0.35);

  box(sl, "Nerve fibers go through CERVICAL GANGLIA\n(Superior, Middle, and Inferior Cervical Ganglia)", 3.9, 3.05, 5.5, 0.75, C.accent2, C.textDark, 12);
  arrowDown(sl, 6.65, 3.8, 0.35);

  box(sl, "Releases NOREPINEPHRINE (Noradrenaline)\nat SA Node", 4.3, 4.15, 4.7, 0.75, C.accent3, C.textDark, 13);
  arrowDown(sl, 6.65, 4.9, 0.35);

  box(sl, "Binds to β1 (Beta-1) Adrenergic Receptors\non SA node cells", 4.3, 5.25, 4.7, 0.7, C.midBg, C.white, 12);
  arrowDown(sl, 6.65, 5.95, 0.35);

  // Two mechanisms
  sl.addShape("line", { x: 6.65, y: 6.3, w: -2.8, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 6.65, y: 6.3, w: 2.8, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 3.85, y: 6.3, w: 0, h: 0.35, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  sl.addShape("line", { x: 9.45, y: 6.3, w: 0, h: 0.35, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  box(sl, "↑ Phase 4 depolarization rate\n(↑ If — funny current)", 2.0, 6.65, 3.7, 0.7, C.accent4, C.textDark, 11);
  box(sl, "↓ Threshold potential\n(↑ ICa — Ca2+ current)", 7.6, 6.65, 3.7, 0.7, C.accent4, C.textDark, 11);
}

// ═══════════════════════════════════════════════════════════════════════════════
// SLIDE 6 — SYMPATHETIC FINAL EFFECT
// ═══════════════════════════════════════════════════════════════════════════════
{
  const sl = pres.addSlide();
  sl.background = { color: C.lightBg };
  sectionHeader(sl, "SYMPATHETIC SYSTEM — FINAL OUTCOME & POSITIVE CHRONOTROPIC EFFECT", C.accent5);

  box(sl, "β1 Receptor Activation by Norepinephrine", 4.3, 0.75, 4.7, 0.7, C.accent5, C.white, 13);
  arrowDown(sl, 6.65, 1.45, 0.35);

  box(sl, "Gs Protein Activated   →   Adenylyl Cyclase Activated   →   ↑ cAMP", 3.0, 1.8, 7.3, 0.7, C.midBg, C.white, 12);
  arrowDown(sl, 6.65, 2.5, 0.35);

  // Two effects
  sl.addShape("line", { x: 6.65, y: 2.85, w: -3.2, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 6.65, y: 2.85, w: 3.2, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 3.45, y: 2.85, w: 0, h: 0.35, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  sl.addShape("line", { x: 9.85, y: 2.85, w: 0, h: 0.35, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  box(sl, "↑ If (Inward Na+ current)\nFaster Phase 4 depolarization\n→ SA node reaches threshold FASTER", 1.5, 3.2, 3.9, 1.0, C.accent2, C.textDark, 11);
  box(sl, "↑ ICa (Ca2+ current)\nThreshold potential DECREASES\n→ Less depolarization needed", 7.9, 3.2, 3.9, 1.0, C.accent2, C.textDark, 11);

  // Converge
  sl.addShape("line", { x: 3.45, y: 4.2, w: 0, h: 0.35, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 9.85, y: 4.2, w: 0, h: 0.35, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 3.45, y: 4.55, w: 6.4, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  arrowDown(sl, 6.65, 4.55, 0.35);

  box(sl, "SA Node fires ACTION POTENTIALS more FREQUENTLY", 4.0, 4.9, 5.3, 0.7, C.accent3, C.textDark, 13);
  arrowDown(sl, 6.65, 5.6, 0.35);

  box(sl, "POSITIVE CHRONOTROPIC EFFECT\n↑ HEART RATE (TACHYCARDIA)", 4.0, 5.95, 5.3, 0.85, C.accent5, C.white, 16, true);
}

// ═══════════════════════════════════════════════════════════════════════════════
// SLIDE 7 — PARASYMPATHETIC SYSTEM (DECREASES HEART RATE)
// ═══════════════════════════════════════════════════════════════════════════════
{
  const sl = pres.addSlide();
  sl.background = { color: C.lightBg };
  sectionHeader(sl, "NERVOUS REGULATION — PARASYMPATHETIC SYSTEM (Decreases Heart Rate)", C.accentPu);

  box(sl, "PARASYMPATHETIC NERVOUS SYSTEM\n(Cardioinhibitory Nerves — Vagus Nerve X)", 4.0, 0.75, 5.3, 0.8, C.accentPu, C.white, 14);
  arrowDown(sl, 6.65, 1.55, 0.35);

  box(sl, "Originates in Cardioinhibitory Center (CIC)\nin Medulla Oblongata", 4.3, 1.9, 4.7, 0.7, C.midBg, C.white, 12);
  arrowDown(sl, 6.65, 2.6, 0.35);

  box(sl, "Vagus Nerve (10th Cranial Nerve)\nReaches SA Node and AV Node", 4.3, 2.95, 4.7, 0.7, C.accent2, C.textDark, 12);
  arrowDown(sl, 6.65, 3.65, 0.35);

  box(sl, "Releases ACETYLCHOLINE (ACh)\nat SA Node", 4.3, 4.0, 4.7, 0.7, C.accent3, C.textDark, 13);
  arrowDown(sl, 6.65, 4.7, 0.35);

  box(sl, "Binds to M2 (Muscarinic) Receptors\non SA node cells", 4.3, 5.05, 4.7, 0.7, C.midBg, C.white, 12);
  arrowDown(sl, 6.65, 5.75, 0.35);

  // Three branches
  sl.addShape("line", { x: 6.65, y: 6.1, w: -4.5, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 6.65, y: 6.1, w: 4.5, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  arrowDown(sl, 6.65, 6.1, 0.35);
  sl.addShape("line", { x: 2.15, y: 6.1, w: 0, h: 0.35, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  sl.addShape("line", { x: 11.15, y: 6.1, w: 0, h: 0.35, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  box(sl, "↓ If\n(Slows Phase 4\ndepolarization)", 0.4, 6.45, 3.5, 0.8, C.accent2, C.textDark, 11);
  box(sl, "↑ IK-ACh\n(Hyperpolarizes\nmax diastolic potential)", 4.9, 6.45, 3.5, 0.8, C.accent2, C.textDark, 11);
  box(sl, "↓ ICa\n(Raises threshold\npotential)", 9.45, 6.45, 3.4, 0.8, C.accent2, C.textDark, 11);
}

// ═══════════════════════════════════════════════════════════════════════════════
// SLIDE 8 — PARASYMPATHETIC FINAL EFFECT
// ═══════════════════════════════════════════════════════════════════════════════
{
  const sl = pres.addSlide();
  sl.background = { color: C.lightBg };
  sectionHeader(sl, "PARASYMPATHETIC SYSTEM — FINAL OUTCOME & NEGATIVE CHRONOTROPIC EFFECT", C.accentPu);

  box(sl, "THREE Combined Effects of ACh on SA Node", 4.0, 0.75, 5.3, 0.65, C.accentPu, C.white, 13);
  arrowDown(sl, 6.65, 1.4, 0.35);

  sl.addShape("line", { x: 6.65, y: 1.75, w: -4.0, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 6.65, y: 1.75, w: 4.0, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  arrowDown(sl, 6.65, 1.75, 0.35);
  sl.addShape("line", { x: 2.65, y: 1.75, w: 0, h: 0.35, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  sl.addShape("line", { x: 10.65, y: 1.75, w: 0, h: 0.35, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });

  box(sl, "Effect 1:\nSLOWS Phase 4\ndepolarization rate", 1.0, 2.1, 3.3, 0.9, C.accent2, C.textDark, 11);
  box(sl, "Effect 2:\nHyperpolarizes\nmax diastolic potential\n(SA node further from threshold)", 4.9, 2.1, 3.5, 1.2, C.accent2, C.textDark, 10);
  box(sl, "Effect 3:\nIncreases threshold\npotential\n(more depolarization needed)", 9.2, 2.1, 3.6, 1.2, C.accent2, C.textDark, 10);

  // Converge
  sl.addShape("line", { x: 2.65, y: 3.0, w: 0, h: 0.4, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 6.65, y: 3.3, w: 0, h: 0.1, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 10.95, y: 3.3, w: 0, h: 0.1, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 2.65, y: 3.4, w: 8.3, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  arrowDown(sl, 6.65, 3.4, 0.4);

  box(sl, "SA Node fires ACTION POTENTIALS LESS frequently\n(SA node depolarized to threshold LESS often)", 3.8, 3.8, 5.7, 0.75, C.accent3, C.textDark, 12);
  arrowDown(sl, 6.65, 4.55, 0.35);

  box(sl, "NEGATIVE CHRONOTROPIC EFFECT\n↓ HEART RATE (BRADYCARDIA)", 4.0, 4.9, 5.3, 0.85, C.accentPu, C.white, 16, true);
  arrowDown(sl, 6.65, 5.75, 0.35);

  box(sl, "Vagal Tone — Parasympathetic dominates at REST → Normal resting HR ~72 beats/min", 2.5, 6.1, 8.3, 0.7, C.accent1, C.white, 12);
}

// ═══════════════════════════════════════════════════════════════════════════════
// SLIDE 9 — CARDIOVASCULAR CENTER IN MEDULLA (Control Center)
// ═══════════════════════════════════════════════════════════════════════════════
{
  const sl = pres.addSlide();
  sl.background = { color: C.lightBg };
  sectionHeader(sl, "CARDIOVASCULAR CENTER IN MEDULLA — CONTROL OF HEART RATE", C.midBg);

  box(sl, "CARDIOVASCULAR CENTER\n(Vasomotor Center — Medulla Oblongata)", 4.0, 0.75, 5.3, 0.8, C.accent1, C.white, 14);
  arrowDown(sl, 6.65, 1.55, 0.35);

  // Two sub-centers
  sl.addShape("line", { x: 6.65, y: 1.9, w: -3.5, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 6.65, y: 1.9, w: 3.5, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 3.15, y: 1.9, w: 0, h: 0.35, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  sl.addShape("line", { x: 10.15, y: 1.9, w: 0, h: 0.35, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  box(sl, "CARDIOACCELERATOR\nCENTER (CAC)\n— Sympathetic", 1.5, 2.25, 3.3, 0.95, C.accent5, C.white, 12);
  box(sl, "CARDIOINHIBITORY\nCENTER (CIC)\n— Parasympathetic", 8.5, 2.25, 3.3, 0.95, C.accentPu, C.white, 12);

  // Inputs to cardiovascular center
  sl.addText("INPUTS TO CARDIOVASCULAR CENTER:", {
    x: 0.5, y: 3.45, w: 12.3, h: 0.4,
    fontSize: 13, bold: true, color: C.textDark, align: "center", fontFace: "Calibri"
  });

  const inputs = [
    { label: "BARORECEPTORS\n(Aortic arch & Carotid sinus)\n↑ BP → ↓ HR (vagal reflex)", x: 0.3, y: 3.9, color: C.accent2 },
    { label: "CHEMORECEPTORS\n(↓ O2, ↑ CO2, ↑ H+)\n→ ↑ HR initially", x: 3.5, y: 3.9, color: C.accent3 },
    { label: "HIGHER BRAIN\nCENTERS\n(Cortex, Hypothalamus)", x: 6.7, y: 3.9, color: C.accentPu },
    { label: "BAINBRIDGE\nREFLEX\n(↑ Venous return → ↑ HR)", x: 9.9, y: 3.9, color: C.accent4 },
  ];
  inputs.forEach(inp => {
    box(sl, inp.label, inp.x, inp.y, 3.1, 1.0, inp.color, inp.color === C.accent3 || inp.color === C.accent2 ? C.textDark : C.white, 11);
    sl.addShape("line", { x: inp.x + 1.55, y: inp.y, w: 0, h: -0.5, line: { color: C.arrowClr, width: 1.6, endArrowType: "triangle" } });
  });

  arrowDown(sl, 6.65, 4.9, 0.35);
  box(sl, "Cardiovascular Center integrates ALL inputs → adjusts Sympathetic / Parasympathetic output → Controls SA Node → Sets Heart Rate", 0.8, 5.25, 11.7, 0.8, C.accent1, C.white, 12);
}

// ═══════════════════════════════════════════════════════════════════════════════
// SLIDE 10 — HORMONAL REGULATION
// ═══════════════════════════════════════════════════════════════════════════════
{
  const sl = pres.addSlide();
  sl.background = { color: C.lightBg };
  sectionHeader(sl, "HORMONAL REGULATION OF HEART RATE", C.accentPu);

  box(sl, "HORMONES AFFECTING HEART RATE", 4.15, 0.75, 5.0, 0.7, C.accentPu, C.white, 15);
  arrowDown(sl, 6.65, 1.45, 0.35);

  // Split into two columns: increase vs decrease
  sl.addShape("rect", { x: 0.3, y: 1.8, w: 5.8, h: 0.45, fill: { color: C.accent5 }, line: { color: C.accent5 } });
  sl.addText("HORMONES THAT ↑ HEART RATE", { x: 0.3, y: 1.8, w: 5.8, h: 0.45, fontSize: 13, bold: true, color: C.white, align: "center", valign: "middle", fontFace: "Calibri" });
  sl.addShape("rect", { x: 7.2, y: 1.8, w: 5.8, h: 0.45, fill: { color: C.accentPu }, line: { color: C.accentPu } });
  sl.addText("HORMONES THAT ↓ HEART RATE", { x: 7.2, y: 1.8, w: 5.8, h: 0.45, fontSize: 13, bold: true, color: C.white, align: "center", valign: "middle", fontFace: "Calibri" });

  const increaseHormones = [
    ["Epinephrine (Adrenaline)", "Adrenal medulla → β1 receptors → ↑ HR (similar to sympathetic)"],
    ["Norepinephrine", "Adrenal medulla → β1 receptors → ↑ HR"],
    ["Thyroid Hormones (T3/T4)", "↑ sensitivity of heart to catecholamines → ↑ HR"],
    ["Glucagon", "Acts on SA node → ↑ HR (less potent)"],
  ];

  const decreaseHormones = [
    ["Acetylcholine (ACh)", "Vagal stimulation → M2 receptors → ↓ HR"],
    ["Adenosine", "Acts on A1 receptors → ↓ HR (used clinically for SVT)"],
    ["High Progesterone", "Mild bradycardia in some contexts"],
  ];

  let y = 2.35;
  increaseHormones.forEach(h => {
    box(sl, h[0], 0.3, y, 2.4, 0.6, C.accent5, C.white, 11);
    sl.addShape("line", { x: 2.7, y: y + 0.3, w: 0.4, h: 0, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
    box(sl, h[1], 3.1, y, 3.0, 0.6, "FFF3E0", C.textDark, 10, false);
    y += 0.7;
  });

  y = 2.35;
  decreaseHormones.forEach(h => {
    box(sl, h[0], 7.2, y, 2.4, 0.6, C.accentPu, C.white, 11);
    sl.addShape("line", { x: 9.6, y: y + 0.3, w: 0.4, h: 0, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
    box(sl, h[1], 10.0, y, 3.0, 0.6, "EDE7F6", C.textDark, 10, false);
    y += 0.7;
  });

  box(sl, "KEY POINT: Epinephrine and Norepinephrine from adrenal medulla mimic sympathetic stimulation — both act on β1 receptors of SA node to increase heart rate", 0.5, 5.8, 12.3, 0.85, C.accent1, C.white, 12);
}

// ═══════════════════════════════════════════════════════════════════════════════
// SLIDE 11 — TEMPERATURE & CHEMICAL FACTORS
// ═══════════════════════════════════════════════════════════════════════════════
{
  const sl = pres.addSlide();
  sl.background = { color: C.lightBg };
  sectionHeader(sl, "TEMPERATURE, CHEMICAL & IONIC FACTORS AFFECTING HEART RATE", C.accent3);

  // Temperature section
  box(sl, "BODY TEMPERATURE", 0.4, 0.75, 3.5, 0.6, C.accent3, C.textDark, 14);
  arrowDown(sl, 2.15, 1.35, 0.35);

  sl.addShape("line", { x: 2.15, y: 1.7, w: -1.3, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 2.15, y: 1.7, w: 1.3, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 0.85, y: 1.7, w: 0, h: 0.35, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  sl.addShape("line", { x: 3.45, y: 1.7, w: 0, h: 0.35, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  box(sl, "↑ Temp (FEVER)\n→ ↑ Heart Rate\n(10 bpm per 1°F rise)", 0.2, 2.05, 1.3, 0.85, C.accent5, C.white, 10);
  box(sl, "↓ Temp (HYPOTHERMIA)\n→ ↓ Heart Rate\n(Bradycardia)", 2.55, 2.05, 1.3, 0.85, C.accentPu, C.white, 10);

  box(sl, "Mechanism: Temperature changes directly affect\nmetabolic rate of SA node cells", 0.2, 3.0, 3.7, 0.7, C.accent2, C.textDark, 10);

  // Chemical factors section
  box(sl, "BLOOD GAS LEVELS (O2 / CO2)", 4.5, 0.75, 4.3, 0.6, C.accent3, C.textDark, 13);
  arrowDown(sl, 6.65, 1.35, 0.35);

  sl.addShape("line", { x: 6.65, y: 1.7, w: -1.5, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 6.65, y: 1.7, w: 1.5, h: 0, line: { color: C.arrowClr, width: 1.8 } });
  sl.addShape("line", { x: 5.15, y: 1.7, w: 0, h: 0.35, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  sl.addShape("line", { x: 8.15, y: 1.7, w: 0, h: 0.35, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  box(sl, "HYPOXIA (↓ O2)\n↑ CO2, ↑ H+\n(Acidosis)\n→ ↑ HR via chemoreceptors", 4.0, 2.05, 2.3, 1.0, C.accent5, C.white, 10);
  box(sl, "↑ O2\n↓ CO2 (Alkalosis)\n→ ↓ HR\n(Less chemoreceptor drive)", 6.9, 2.05, 2.3, 1.0, C.accentPu, C.white, 10);

  // Ions section
  box(sl, "ELECTROLYTE (ION) EFFECTS", 9.5, 0.75, 3.5, 0.6, C.accent3, C.textDark, 13);
  arrowDown(sl, 11.25, 1.35, 0.35);

  const ions = [
    ["↑ K+ (Hyperkalemia)", "↓ HR → Cardiac arrest (extreme)", "E3F2FD"],
    ["↓ K+ (Hypokalemia)", "↑ HR → Arrhythmia risk", "FFEBEE"],
    ["↑ Ca2+ (Hypercalcemia)", "↑ HR → Spastic heart", "FFEBEE"],
    ["↓ Ca2+ (Hypocalcemia)", "↓ HR → Tetany, bradycardia", "E3F2FD"],
  ];
  ions.forEach((ion, i) => {
    box(sl, ion[0] + "\n→ " + ion[1], 9.0, 1.7 + i * 0.75, 4.5, 0.65, ion[2] === "E3F2FD" ? C.accent2 : C.accent5, ion[2] === "E3F2FD" ? C.textDark : C.white, 10, false);
  });

  // Exercise section at bottom
  box(sl, "EXERCISE & PHYSICAL ACTIVITY → ↑ HR (via sympathetic activation + ↓ vagal tone + ↑ CO2 / ↓ O2 in muscles)", 0.3, 4.8, 12.7, 0.65, C.accent4, C.textDark, 12);
  arrowDown(sl, 6.65, 5.45, 0.35);
  box(sl, "Maximum HR during exercise = 220 − Age (years) [approximate formula]", 3.0, 5.8, 7.3, 0.6, C.midBg, C.white, 12);
}

// ═══════════════════════════════════════════════════════════════════════════════
// SLIDE 12 — AGE, SEX, AND OTHER FACTORS
// ═══════════════════════════════════════════════════════════════════════════════
{
  const sl = pres.addSlide();
  sl.background = { color: C.lightBg };
  sectionHeader(sl, "AGE, SEX, EMOTIONAL & OTHER FACTORS AFFECTING HEART RATE", C.accent4);

  // Age
  box(sl, "AGE", 0.3, 0.75, 2.0, 0.6, C.accent4, C.textDark, 14);
  arrowDown(sl, 1.3, 1.35, 0.35);
  const ageData = [
    ["Fetus (in womb)", "120–160 bpm"],
    ["Newborn", "~120 bpm"],
    ["Infant (1 yr)", "~110 bpm"],
    ["Child (5 yrs)", "~90 bpm"],
    ["Adult (20–60 yrs)", "60–100 bpm"],
    ["Elderly (>60 yrs)", "Slightly ↑ due to ↓ vagal tone"],
  ];
  ageData.forEach((d, i) => {
    box(sl, d[0], 0.2, 1.7 + i * 0.72, 1.5, 0.62, i % 2 === 0 ? C.accent2 : C.midBg, i % 2 === 0 ? C.textDark : C.white, 10, false);
    sl.addShape("line", { x: 1.7, y: 1.7 + i * 0.72 + 0.31, w: 0.3, h: 0, line: { color: C.arrowClr, width: 1.6, endArrowType: "triangle" } });
    box(sl, d[1], 2.0, 1.7 + i * 0.72, 1.5, 0.62, "F1F8E9", C.textDark, 10, false);
  });

  // Sex
  box(sl, "SEX", 4.5, 0.75, 2.0, 0.6, C.accentPu, C.white, 14);
  arrowDown(sl, 5.5, 1.35, 0.35);
  box(sl, "Females have slightly HIGHER resting HR than males\n(~5–7 bpm higher on average)", 3.8, 1.7, 3.4, 0.9, C.accentPu, C.white, 11);
  arrowDown(sl, 5.5, 2.6, 0.35);
  box(sl, "Due to smaller heart size → lower stroke volume\n→ higher HR needed to maintain cardiac output", 3.8, 2.95, 3.4, 0.9, "EDE7F6", C.textDark, 10, false);

  // Emotions / Psychological
  box(sl, "EMOTIONAL & PSYCHOLOGICAL FACTORS", 8.3, 0.75, 4.7, 0.6, C.accent5, C.white, 13);
  arrowDown(sl, 10.65, 1.35, 0.35);
  const emotions = [
    { e: "Fear / Anxiety", effect: "↑ HR (sympathetic activation)", color: C.accent5 },
    { e: "Excitement", effect: "↑ HR (adrenaline rush)", color: C.accent5 },
    { e: "Grief / Sorrow", effect: "↓ HR (vagal dominance)", color: C.accentPu },
    { e: "Deep Sleep", effect: "↓ HR (parasympathetic dominates)", color: C.accentPu },
  ];
  emotions.forEach((em, i) => {
    box(sl, em.e + "\n→ " + em.effect, 8.1, 1.7 + i * 0.72, 4.9, 0.62, em.color, C.white, 10, false);
  });

  // Posture & Others at bottom
  box(sl, "POSTURE", 0.3, 6.0, 1.8, 0.55, C.accent3, C.textDark, 12);
  sl.addShape("line", { x: 2.1, y: 6.27, w: 0.5, h: 0, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  box(sl, "Standing → ↑ HR vs lying down (orthostatic reflex)", 2.6, 6.0, 4.6, 0.55, "FFF8E1", C.textDark, 11, false);

  box(sl, "PAIN", 7.5, 6.0, 1.3, 0.55, C.accent3, C.textDark, 12);
  sl.addShape("line", { x: 8.8, y: 6.27, w: 0.5, h: 0, line: { color: C.arrowClr, width: 1.8, endArrowType: "triangle" } });
  box(sl, "Acute pain → ↑ HR (sympathetic)  |  Severe/chronic pain → ↓ HR (vasovagal)", 9.3, 6.0, 3.7, 0.55, "FFF8E1", C.textDark, 10, false);
}

// ═══════════════════════════════════════════════════════════════════════════════
// SLIDE 13 — REFLEXES CONTROLLING HEART RATE
// ═══════════════════════════════════════════════════════════════════════════════
{
  const sl = pres.addSlide();
  sl.background = { color: C.lightBg };
  sectionHeader(sl, "REFLEXES CONTROLLING HEART RATE", C.accent1);

  // Bainbridge Reflex
  box(sl, "BAINBRIDGE REFLEX\n(Atrial Reflex)", 0.3, 0.8, 3.2, 0.75, C.accent1, C.white, 13);
  arrowDown(sl, 1.9, 1.55, 0.35);
  box(sl, "↑ Venous return\n→ Stretches right atrium", 0.3, 1.9, 3.2, 0.7, C.accent2, C.textDark, 11);
  arrowDown(sl, 1.9, 2.6, 0.35);
  box(sl, "Stretch receptors (atrial mechanoreceptors)\nsend signals to medulla via vagus nerve", 0.3, 2.95, 3.2, 0.75, C.midBg, C.white, 10, false);
  arrowDown(sl, 1.9, 3.7, 0.35);
  box(sl, "↑ Sympathetic + ↓ Parasympathetic\n→ ↑ HEART RATE", 0.3, 4.05, 3.2, 0.7, C.accent5, C.white, 11);
  box(sl, "Purpose: Prevent blood pooling in veins; match HR with increased venous return", 0.3, 4.85, 3.2, 0.75, "E3F2FD", C.textDark, 10, false);

  // Baroreceptor Reflex
  box(sl, "BARORECEPTOR REFLEX\n(Carotid Sinus / Aortic Arch)", 5.05, 0.8, 3.2, 0.75, C.accent3, C.textDark, 13);
  arrowDown(sl, 6.65, 1.55, 0.35);
  box(sl, "↑ Blood Pressure\n→ Stretches arterial walls", 5.05, 1.9, 3.2, 0.7, C.accent2, C.textDark, 11);
  arrowDown(sl, 6.65, 2.6, 0.35);
  box(sl, "Baroreceptors signal CIC in medulla\nvia Glossopharyngeal (IX) & Vagus (X) nerves", 5.05, 2.95, 3.2, 0.75, C.midBg, C.white, 10, false);
  arrowDown(sl, 6.65, 3.7, 0.35);
  box(sl, "↑ Parasympathetic + ↓ Sympathetic\n→ ↓ HEART RATE (Reflex Bradycardia)", 5.05, 4.05, 3.2, 0.7, C.accentPu, C.white, 11);
  box(sl, "Purpose: Prevent dangerously high BP; buffer BP changes (short-term)", 5.05, 4.85, 3.2, 0.75, "EDE7F6", C.textDark, 10, false);

  // Chemoreceptor Reflex
  box(sl, "CHEMORECEPTOR REFLEX\n(Carotid & Aortic Bodies)", 9.8, 0.8, 3.2, 0.75, C.accent4, C.textDark, 13);
  arrowDown(sl, 11.4, 1.55, 0.35);
  box(sl, "↓ O2 (Hypoxia)\n↑ CO2 / ↑ H+ (Acidosis)", 9.8, 1.9, 3.2, 0.7, C.accent2, C.textDark, 11);
  arrowDown(sl, 11.4, 2.6, 0.35);
  box(sl, "Chemoreceptors activated\n→ Signal to CAC in medulla", 9.8, 2.95, 3.2, 0.75, C.midBg, C.white, 10, false);
  arrowDown(sl, 11.4, 3.7, 0.35);
  box(sl, "↑ Sympathetic drive\n→ ↑ HEART RATE\n(+ Vasoconstriction)", 9.8, 4.05, 3.2, 0.7, C.accent5, C.white, 11);
  box(sl, "Purpose: Increase O2 delivery during hypoxia/acidosis; ensures adequate cardiac output", 9.8, 4.85, 3.2, 0.75, "E8F5E9", C.textDark, 10, false);

  // Bottom summary box
  box(sl, "ALL REFLEXES converge at the Cardiovascular Center (Medulla) → Modulate Sympathetic / Parasympathetic outflow → Change SA Node firing rate → Change Heart Rate", 0.3, 5.8, 12.7, 0.8, C.accent1, C.white, 12);
}

// ═══════════════════════════════════════════════════════════════════════════════
// SLIDE 14 — MASTER SUMMARY FLOWCHART
// ═══════════════════════════════════════════════════════════════════════════════
{
  const sl = pres.addSlide();
  sl.background = { color: C.lightBg };
  sectionHeader(sl, "MASTER SUMMARY — HEART RATE REGULATION (All Factors)", C.darkBg);

  // Top: Stimuli
  const stimuli = [
    { t: "Fear/\nExercise/\nFever", x: 0.2, color: C.accent5 },
    { t: "↓O2\n↑CO2\nAcidosis", x: 2.2, color: C.accent3 },
    { t: "↑ Venous\nReturn\n(Bainbridge)", x: 4.2, color: C.accent4 },
    { t: "↓ Blood\nPressure", x: 6.2, color: C.accentPu },
    { t: "Drugs:\nAtropine /\nAdrenaline", x: 8.2, color: C.accent1 },
    { t: "Emotions /\nAnxiety /\nPain", x: 10.3, color: C.accent5 },
  ];
  stimuli.forEach(s => {
    box(sl, s.t, s.x, 0.75, 1.9, 0.85, s.color, s.color === C.accent3 || s.color === C.accent4 ? C.textDark : C.white, 9);
    arrowDown(sl, s.x + 0.95, 1.6, 0.35);
  });

  // Cardiovascular Center
  box(sl, "CARDIOVASCULAR CENTER (Medulla Oblongata)", 2.5, 1.95, 8.3, 0.65, C.midBg, C.white, 13);
  arrowDown(sl, 6.65, 2.6, 0.35);

  // Two arms: Sympathetic and Parasympathetic
  sl.addShape("line", { x: 6.65, y: 2.95, w: -3.5, h: 0, line: { color: C.arrowClr, width: 2.0 } });
  sl.addShape("line", { x: 6.65, y: 2.95, w: 3.5, h: 0, line: { color: C.arrowClr, width: 2.0 } });
  sl.addShape("line", { x: 3.15, y: 2.95, w: 0, h: 0.35, line: { color: C.arrowClr, width: 2.0, endArrowType: "triangle" } });
  sl.addShape("line", { x: 10.15, y: 2.95, w: 0, h: 0.35, line: { color: C.arrowClr, width: 2.0, endArrowType: "triangle" } });
  box(sl, "↑ SYMPATHETIC\n(Norepinephrine → β1)", 1.5, 3.3, 3.3, 0.75, C.accent5, C.white, 12);
  box(sl, "↓ PARASYMPATHETIC\n(ACh → M2)", 8.5, 3.3, 3.3, 0.75, C.accentPu, C.white, 12);

  // Both converge on SA NODE
  sl.addShape("line", { x: 3.15, y: 4.05, w: 0, h: 0.35, line: { color: C.arrowClr, width: 2.0 } });
  sl.addShape("line", { x: 10.15, y: 4.05, w: 0, h: 0.35, line: { color: C.arrowClr, width: 2.0 } });
  sl.addShape("line", { x: 3.15, y: 4.4, w: 7.0, h: 0, line: { color: C.arrowClr, width: 2.0 } });
  arrowDown(sl, 6.65, 4.4, 0.35);

  box(sl, "SA NODE (Pacemaker)\nSets firing rate", 4.8, 4.75, 3.7, 0.75, C.accent1, C.white, 13);
  arrowDown(sl, 6.65, 5.5, 0.35);

  // Two final outcomes
  sl.addShape("line", { x: 6.65, y: 5.85, w: -3.2, h: 0, line: { color: C.arrowClr, width: 2.0 } });
  sl.addShape("line", { x: 6.65, y: 5.85, w: 3.2, h: 0, line: { color: C.arrowClr, width: 2.0 } });
  sl.addShape("line", { x: 3.45, y: 5.85, w: 0, h: 0.35, line: { color: C.arrowClr, width: 2.0, endArrowType: "triangle" } });
  sl.addShape("line", { x: 9.85, y: 5.85, w: 0, h: 0.35, line: { color: C.arrowClr, width: 2.0, endArrowType: "triangle" } });
  box(sl, "↑ HEART RATE\nTACHYCARDIA\n> 100 bpm", 1.5, 6.2, 3.9, 0.9, C.accent5, C.white, 14);
  box(sl, "↓ HEART RATE\nBRADYCARDIA\n< 60 bpm", 7.9, 6.2, 3.9, 0.9, C.accentPu, C.white, 14);
}

// ═══════════════════════════════════════════════════════════════════════════════
// SLIDE 15 — TRAINING AND HEART RATE (Athletes)
// ═══════════════════════════════════════════════════════════════════════════════
{
  const sl = pres.addSlide();
  sl.background = { color: C.lightBg };
  sectionHeader(sl, "CARDIAC TRAINING EFFECT & HEART RATE IN SPECIAL CONDITIONS", C.accent4);

  // Athlete bradycardia
  box(sl, "ATHLETIC TRAINING EFFECT", 4.3, 0.75, 4.7, 0.65, C.accent4, C.textDark, 14);
  arrowDown(sl, 6.65, 1.4, 0.35);
  box(sl, "Regular aerobic exercise over months/years", 4.3, 1.75, 4.7, 0.6, C.midBg, C.white, 12);
  arrowDown(sl, 6.65, 2.35, 0.35);
  box(sl, "↑ Stroke volume (larger heart, stronger contraction)", 4.3, 2.7, 4.7, 0.6, C.accent2, C.textDark, 12);
  arrowDown(sl, 6.65, 3.3, 0.35);
  box(sl, "Cardiac output maintained with LOWER heart rate", 4.3, 3.65, 4.7, 0.6, C.accent4, C.textDark, 12);
  arrowDown(sl, 6.65, 4.25, 0.35);
  box(sl, "ATHLETE'S BRADYCARDIA\nResting HR = 40–60 bpm (PHYSIOLOGICAL — not pathological)", 4.0, 4.6, 5.3, 0.85, C.accent4, C.textDark, 13);

  // Other special conditions table
  sl.addText("HEART RATE IN SPECIAL CONDITIONS:", { x: 0.5, y: 5.65, w: 12.3, h: 0.4, fontSize: 13, bold: true, color: C.textDark, align: "center", fontFace: "Calibri" });
  const conditions = [
    ["Condition", "HR Change", "Reason"],
    ["Fever (each 1°F rise)", "↑ ~10 bpm", "↑ SA node metabolic rate"],
    ["Hyperthyroidism", "↑↑ HR (>100 bpm)", "T3/T4 sensitize to catecholamines"],
    ["Hypothyroidism", "↓ HR (<60 bpm)", "↓ Catecholamine sensitivity"],
    ["Anemia", "↑ HR", "Compensate for ↓ O2 carrying capacity"],
    ["Heart Block", "↓ HR (30–40 bpm)", "AV block — ventricles use own pacemaker"],
  ];
  conditions.forEach((row, i) => {
    const y = 6.05 + i * 0.21;
    const colors = i === 0 ? [C.midBg, C.midBg, C.midBg] : [C.lightBg, "FFF8E1", "E8F5E9"];
    const textClrs = i === 0 ? [C.white, C.white, C.white] : [C.textDark, C.textDark, C.textDark];
    [row[0], row[1], row[2]].forEach((cell, j) => {
      sl.addShape("rect", { x: 0.5 + j * 4.1, y, w: 4.0, h: 0.2, fill: { color: colors[j] }, line: { color: C.gray, width: 0.5 } });
      sl.addText(cell, { x: 0.5 + j * 4.1, y, w: 4.0, h: 0.2, fontSize: 9, bold: i === 0, color: textClrs[j], align: "center", valign: "middle", fontFace: "Calibri" });
    });
  });
}

// ═══════════════════════════════════════════════════════════════════════════════
// WRITE FILE
// ═══════════════════════════════════════════════════════════════════════════════
pres.writeFile({ fileName: "/home/daytona/workspace/heart-rate-flowcharts/Heart_Rate_Flowcharts_Sembulingam.pptx" })
  .then(() => console.log("SUCCESS: File written!"))
  .catch(err => console.error("ERROR:", err));