/* ========== RESET & BASE ========== */
*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: 20px;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  background: #0f1117;
  color: #e1e4ea;
  line-height: 1.7;
  overflow-x: hidden;
}

a {
  color: #60a5fa;
  text-decoration: none;
  transition: color 0.2s;
}

a:hover {
  color: #93c5fd;
}

code {
  font-family: 'Fira Code', monospace;
  background: rgba(99, 102, 241, 0.15);
  color: #a5b4fc;
  padding: 2px 7px;
  border-radius: 5px;
  font-size: 0.88em;
}

.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ========== HERO ========== */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  background: linear-gradient(135deg, #0f172a 0%, #1e1b4b 40%, #312e81 70%, #1e3a5f 100%);
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background:
    radial-gradient(600px circle at 20% 30%, rgba(99, 102, 241, 0.15), transparent 50%),
    radial-gradient(500px circle at 80% 70%, rgba(59, 130, 246, 0.12), transparent 50%),
    radial-gradient(300px circle at 50% 50%, rgba(168, 85, 247, 0.08), transparent 50%);
  pointer-events: none;
}

.hero-overlay {
  position: absolute;
  inset: 0;
  background: url("data:image/svg+xml,%3Csvg width='60' height='60' xmlns='http://www.w3.org/2000/svg'%3E%3Cdefs%3E%3Cpattern id='grid' width='60' height='60' patternUnits='userSpaceOnUse'%3E%3Cpath d='M 60 0 L 0 0 0 60' fill='none' stroke='rgba(255,255,255,0.03)' stroke-width='1'/%3E%3C/pattern%3E%3C/defs%3E%3Crect width='60' height='60' fill='url(%23grid)'/%3E%3C/svg%3E");
  pointer-events: none;
}

.hero-content {
  position: relative;
  z-index: 2;
  padding: 40px 24px;
}

.hero-badge {
  display: inline-block;
  background: rgba(99, 102, 241, 0.2);
  color: #a5b4fc;
  padding: 8px 20px;
  border-radius: 50px;
  font-size: 0.85rem;
  font-weight: 600;
  letter-spacing: 1px;
  text-transform: uppercase;
  border: 1px solid rgba(99, 102, 241, 0.3);
  margin-bottom: 24px;
}

.hero h1 {
  font-size: clamp(2.2rem, 5vw, 3.8rem);
  font-weight: 900;
  line-height: 1.15;
  margin-bottom: 20px;
  color: #ffffff;
}

.hero h1 span {
  background: linear-gradient(135deg, #60a5fa, #a78bfa, #818cf8);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-desc {
  max-width: 600px;
  margin: 0 auto 32px;
  font-size: 1.1rem;
  color: #94a3b8;
  line-height: 1.6;
}

.hero-stats {
  display: flex;
  justify-content: center;
  gap: 40px;
  margin-bottom: 40px;
}

.stat {
  text-align: center;
  color: #94a3b8;
  font-size: 0.9rem;
}

.stat strong {
  display: block;
  font-size: 1.4rem;
  color: #e2e8f0;
  margin-bottom: 2px;
}

.btn-start {
  display: inline-block;
  background: linear-gradient(135deg, #6366f1, #8b5cf6);
  color: #fff;
  padding: 14px 36px;
  border-radius: 12px;
  font-size: 1.05rem;
  font-weight: 600;
  transition: all 0.3s;
  box-shadow: 0 4px 20px rgba(99, 102, 241, 0.3);
}

.btn-start:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 30px rgba(99, 102, 241, 0.5);
  color: #fff;
}

/* ========== PROGRESS BAR ========== */
.progress-bar-container {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 4px;
  background: rgba(255, 255, 255, 0.05);
  z-index: 1000;
}

.progress-bar {
  height: 100%;
  width: 0%;
  background: linear-gradient(90deg, #6366f1, #8b5cf6, #a78bfa);
  transition: width 0.15s ease-out;
  border-radius: 0 2px 2px 0;
}

/* ========== TABLE OF CONTENTS ========== */
.toc {
  background: #13151d;
  padding: 60px 0;
  border-bottom: 1px solid rgba(255, 255, 255, 0.05);
}

.toc h2 {
  text-align: center;
  font-size: 1.6rem;
  margin-bottom: 32px;
  color: #e2e8f0;
}

.toc-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 12px;
}

.toc-item {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 14px 18px;
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid rgba(255, 255, 255, 0.06);
  border-radius: 10px;
  color: #c1c7d4;
  font-size: 0.92rem;
  font-weight: 500;
  transition: all 0.25s;
}

.toc-item:hover {
  background: rgba(99, 102, 241, 0.1);
  border-color: rgba(99, 102, 241, 0.3);
  color: #e2e8f0;
  transform: translateX(4px);
}

.toc-num {
  font-family: 'Fira Code', monospace;
  font-size: 0.78rem;
  font-weight: 600;
  color: #6366f1;
  background: rgba(99, 102, 241, 0.12);
  padding: 4px 10px;
  border-radius: 6px;
  min-width: 36px;
  text-align: center;
}

/* ========== MAIN CONTENT ========== */
.main-content {
  padding: 60px 0;
}

/* ========== PART SECTION ========== */
.part {
  margin-bottom: 64px;
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid rgba(255, 255, 255, 0.06);
  border-radius: 16px;
  overflow: hidden;
  transition: border-color 0.3s;
}

.part:hover {
  border-color: rgba(99, 102, 241, 0.2);
}

.part-header {
  padding: 28px 32px;
  background: linear-gradient(135deg, rgba(99, 102, 241, 0.08), rgba(139, 92, 246, 0.05));
  border-bottom: 1px solid rgba(255, 255, 255, 0.06);
}

.part-number {
  display: inline-block;
  font-family: 'Fira Code', monospace;
  font-size: 0.78rem;
  font-weight: 600;
  color: #a78bfa;
  text-transform: uppercase;
  letter-spacing: 1.5px;
  margin-bottom: 8px;
}

.part-header h2 {
  font-size: 1.5rem;
  font-weight: 700;
  color: #f1f5f9;
}

.part-body {
  padding: 32px;
}

.part-body p {
  margin-bottom: 16px;
  color: #b0b8c8;
}

/* ========== CODE BLOCKS ========== */
.code-block {
  background: #1a1d2e;
  border: 1px solid rgba(255, 255, 255, 0.08);
  border-radius: 12px;
  overflow: hidden;
  margin-bottom: 20px;
}

.code-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 10px 16px;
  background: rgba(255, 255, 255, 0.03);
  border-bottom: 1px solid rgba(255, 255, 255, 0.06);
  font-size: 0.82rem;
  color: #6b7280;
}

.copy-btn {
  background: rgba(99, 102, 241, 0.15);
  color: #a5b4fc;
  border: 1px solid rgba(99, 102, 241, 0.25);
  padding: 5px 12px;
  border-radius: 6px;
  font-size: 0.78rem;
  cursor: pointer;
  transition: all 0.2s;
  font-family: 'Inter', sans-serif;
}

.copy-btn:hover {
  background: rgba(99, 102, 241, 0.3);
}

.copy-btn.copied {
  background: rgba(34, 197, 94, 0.2);
  color: #86efac;
  border-color: rgba(34, 197, 94, 0.3);
}

.code-block pre {
  padding: 18px 20px;
  overflow-x: auto;
  font-size: 0.9rem;
  line-height: 1.7;
}

.code-block pre code {
  background: none;
  padding: 0;
  color: #c4cad8;
  font-size: 0.9rem;
}

/* ========== INFO CARDS ========== */
.info-card {
  display: flex;
  align-items: flex-start;
  gap: 16px;
  padding: 18px 22px;
  border-radius: 12px;
  margin-bottom: 20px;
  border: 1px solid;
}

.info-card-icon {
  font-size: 1.4rem;
  flex-shrink: 0;
  margin-top: 2px;
}

.accent-blue {
  background: rgba(59, 130, 246, 0.06);
  border-color: rgba(59, 130, 246, 0.15);
  color: #93aed4;
}

.accent-orange {
  background: rgba(251, 146, 60, 0.06);
  border-color: rgba(251, 146, 60, 0.15);
  color: #d4a884;
}

.accent-purple {
  background: rgba(168, 85, 247, 0.06);
  border-color: rgba(168, 85, 247, 0.15);
  color: #c4a5e0;
}

.accent-green {
  background: rgba(34, 197, 94, 0.06);
  border-color: rgba(34, 197, 94, 0.15);
  color: #86c4a0;
}

/* ========== WARNING CARD ========== */
.warning-card {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 16px 22px;
  background: rgba(245, 158, 11, 0.06);
  border: 1px solid rgba(245, 158, 11, 0.2);
  border-radius: 12px;
  margin-bottom: 20px;
  color: #d4b06c;
}

.warning-icon {
  font-size: 1.3rem;
  flex-shrink: 0;
}

/* ========== SUCCESS CARD ========== */
.success-card {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 16px 22px;
  background: rgba(34, 197, 94, 0.06);
  border: 1px solid rgba(34, 197, 94, 0.2);
  border-radius: 12px;
  margin-bottom: 20px;
  color: #78c99a;
  font-weight: 500;
}

.final-success {
  padding: 24px;
  font-size: 1.05rem;
  background: linear-gradient(135deg, rgba(34, 197, 94, 0.08), rgba(59, 130, 246, 0.06));
  border-color: rgba(34, 197, 94, 0.25);
}

/* ========== HIGHLIGHT BOX ========== */
.highlight-box {
  display: inline-block;
  background: rgba(99, 102, 241, 0.1);
  border: 1px solid rgba(99, 102, 241, 0.2);
  padding: 10px 24px;
  border-radius: 10px;
  font-weight: 600;
  color: #c4b5fd;
  margin-bottom: 20px;
  font-size: 1.05rem;
}

/* ========== DEFINITION CARD ========== */
.definition-card {
  background: linear-gradient(135deg, rgba(99, 102, 241, 0.08), rgba(168, 85, 247, 0.05));
  border: 1px solid rgba(99, 102, 241, 0.2);
  padding: 28px;
  border-radius: 14px;
  text-align: center;
  margin-bottom: 28px;
}

.definition-card h3 {
  font-size: 1.6rem;
  color: #e2e8f0;
  margin-bottom: 8px;
}

.definition-card p {
  color: #94a3b8;
  font-size: 1.05rem;
}

/* ========== FEATURE GRID ========== */
.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 16px;
  margin-bottom: 20px;
}

.feature-card {
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid rgba(255, 255, 255, 0.06);
  padding: 24px;
  border-radius: 14px;
  text-align: center;
  transition: all 0.3s;
}

.feature-card:hover {
  border-color: rgba(99, 102, 241, 0.2);
  transform: translateY(-4px);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.2);
}

.feature-icon {
  font-size: 2rem;
  margin-bottom: 12px;
}

.feature-card h4 {
  color: #e2e8f0;
  margin-bottom: 8px;
  font-size: 1rem;
}

.feature-card p {
  color: #8891a4;
  font-size: 0.88rem;
  line-height: 1.5;
}

/* ========== STEP LIST ========== */
.step-block {
  margin-bottom: 28px;
}

.step-block h3 {
  font-size: 1.15rem;
  color: #d4d9e4;
  margin-bottom: 14px;
}

.step-list {
  padding-left: 24px;
  margin-bottom: 16px;
}

.step-list li {
  margin-bottom: 10px;
  color: #b0b8c8;
  padding-left: 8px;
}

.step-list li::marker {
  color: #6366f1;
  font-weight: 700;
}

/* ========== EXPLANATION BLOCK ========== */
.explanation-block {
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid rgba(255, 255, 255, 0.06);
  border-radius: 14px;
  padding: 24px 28px;
  margin-bottom: 24px;
}

.explanation-block h3 {
  font-size: 1.15rem;
  color: #e2e8f0;
  margin-bottom: 16px;
}

.explain-table {
  width: 100%;
  border-collapse: separate;
  border-spacing: 0;
}

.explain-table thead th {
  text-align: left;
  padding: 12px 16px;
  background: rgba(99, 102, 241, 0.08);
  color: #a5b4fc;
  font-size: 0.85rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.explain-table thead th:first-child {
  border-radius: 8px 0 0 0;
}

.explain-table thead th:last-child {
  border-radius: 0 8px 0 0;
}

.explain-table td {
  padding: 12px 16px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.04);
  color: #b0b8c8;
  font-size: 0.92rem;
}

.explain-table tr:last-child td {
  border-bottom: none;
}

/* ========== SETTINGS TABLE ========== */
.settings-table {
  width: 100%;
  margin-bottom: 20px;
}

.settings-table td {
  padding: 12px 16px;
  vertical-align: middle;
}

.settings-table td:first-child {
  width: 200px;
  color: #94a3b8;
}

/* ========== SUMMARY SECTION ========== */
.summary-section {
  margin-top: 40px;
  padding: 48px 32px;
  background: linear-gradient(135deg, rgba(99, 102, 241, 0.05), rgba(168, 85, 247, 0.03));
  border: 1px solid rgba(99, 102, 241, 0.15);
  border-radius: 16px;
}

.summary-section h2 {
  text-align: center;
  font-size: 1.5rem;
  color: #e2e8f0;
  margin-bottom: 36px;
}

.summary-timeline {
  position: relative;
  padding-left: 32px;
  max-width: 600px;
  margin: 0 auto;
}

.summary-timeline::before {
  content: '';
  position: absolute;
  left: 7px;
  top: 8px;
  bottom: 8px;
  width: 2px;
  background: linear-gradient(to bottom, #6366f1, #a78bfa, #22c55e);
  border-radius: 2px;
}

.timeline-item {
  position: relative;
  margin-bottom: 18px;
  display: flex;
  align-items: flex-start;
  gap: 16px;
}

.timeline-dot {
  position: absolute;
  left: -28px;
  top: 6px;
  width: 12px;
  height: 12px;
  background: #6366f1;
  border-radius: 50%;
  border: 2px solid #0f1117;
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.2);
}

.timeline-dot.last {
  background: #22c55e;
  box-shadow: 0 0 0 3px rgba(34, 197, 94, 0.2);
}

.timeline-content {
  color: #b0b8c8;
  font-size: 0.95rem;
  padding: 4px 0;
}

.timeline-content strong {
  color: #e2e8f0;
}

/* ========== FOOTER ========== */
.footer {
  text-align: center;
  padding: 40px 24px;
  border-top: 1px solid rgba(255, 255, 255, 0.05);
  color: #6b7280;
  font-size: 0.9rem;
}

/* ========== BACK TO TOP ========== */
.back-to-top {
  position: fixed;
  bottom: 32px;
  right: 32px;
  width: 48px;
  height: 48px;
  background: linear-gradient(135deg, #6366f1, #8b5cf6);
  color: #fff;
  border: none;
  border-radius: 14px;
  font-size: 1.3rem;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(12px);
  transition: all 0.3s;
  box-shadow: 0 4px 16px rgba(99, 102, 241, 0.3);
  z-index: 100;
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-to-top:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 24px rgba(99, 102, 241, 0.5);
}

/* ========== ANIMATIONS ========== */
.part {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.part.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ========== RESPONSIVE ========== */
@media (max-width: 768px) {
  .hero-stats {
    flex-direction: column;
    gap: 16px;
  }

  .part-header {
    padding: 20px 20px;
  }

  .part-body {
    padding: 20px;
  }

  .feature-grid {
    grid-template-columns: 1fr;
  }

  .toc-grid {
    grid-template-columns: 1fr;
  }

  .explain-table {
    font-size: 0.85rem;
  }

  .explain-table td,
  .explain-table th {
    padding: 10px 12px;
  }

  .summary-section {
    padding: 32px 20px;
  }

  .back-to-top {
    bottom: 20px;
    right: 20px;
    width: 42px;
    height: 42px;
  }
}

@media (max-width: 480px) {
  .hero h1 {
    font-size: 1.8rem;
  }

  .hero-desc {
    font-size: 0.95rem;
  }

  .settings-table td:first-child {
    width: auto;
  }

  .settings-table td {
    display: block;
    padding: 6px 16px;
  }
}