:root {
  --color-aws-dark: #232F3E;
  --color-aws-orange: #dc7600;
  --color-aws-orange-original: #FF9900;
  --color-aws-orange-hover: #EC7211;
  --color-text-primary: #374151;
  --color-text-secondary: #6B7280;
  --color-text-white: #FFFFFF;
  --color-bg-light: #F9FAFB;
  --color-bg-white: #FFFFFF;
  --color-bg-gradient-start: #232F3E;
  --color-bg-gradient-end: #374151;
  --color-border-light: #E5E7EB;
  --color-success: #10B981;
  --color-warning: #F59E0B;
  --color-error: #EF4444;
  --color-info: #3B82F6;
  --shadow-sm: 0 2px 4px rgba(0,0,0,0.1);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
  --shadow-lg: 0 10px 40px rgba(0,0,0,0.15);
  --radius-sm: 6px;
  --radius-md: 8px;
  --radius-lg: 15px;
  --radius-xl: 20px;
  --transition-base: 0.3s ease;
  --header-height: 60px;
  --container-max-width: 1200px;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Helvetica Neue', Arial, sans-serif;
  line-height: 1.7;
  color: var(--color-text-primary);
  background-color: var(--color-bg-light);
  padding-top: var(--header-height);
  font-size: 20px;
}

/* ===== Progress Bar ===== */
.progress-bar {
  position: fixed; top: var(--header-height); left: 0; width: 0%; height: 4px;
  background: linear-gradient(90deg, var(--color-aws-orange-original), var(--color-aws-orange-hover));
  z-index: 1001; transition: width 0.1s linear;
}

/* ===== Container ===== */
.container {
  max-width: var(--container-max-width); margin: 0 auto; padding: 0;
  background: var(--color-bg-white); border-radius: 16px; box-shadow: var(--shadow-lg);
  overflow: hidden;
}

/* ===== Hero ===== */
.hero {
  background: linear-gradient(135deg, #232F3E 0%, #37475A 50%, #485769 100%);
  color: white; padding: 60px 40px; text-align: center; position: relative; overflow: hidden;
}
.hero::before {
  content: ''; position: absolute; top: -50%; left: -50%; width: 200%; height: 200%;
  background: radial-gradient(circle at 30% 70%, rgba(255,153,0,0.12) 0%, transparent 50%),
              radial-gradient(circle at 70% 30%, rgba(59,130,246,0.08) 0%, transparent 50%);
  pointer-events: none;
}
.hero-badge {
  display: inline-block; background: rgba(255,153,0,0.2); color: var(--color-aws-orange-original);
  padding: 8px 24px; border-radius: 30px; font-size: 0.85em; font-weight: 600;
  margin-bottom: 20px; position: relative;
}
.hero h1 { font-size: 2.2em; font-weight: 700; margin-bottom: 16px; position: relative; color: #fff; }
.hero-subtitle { font-size: 1.1em; opacity: 0.9; max-width: 800px; margin: 0 auto 30px; position: relative; }

/* Hero Stats Row */
.hero-stats {
  display: flex; justify-content: center; gap: 40px; margin-top: 30px;
  position: relative; flex-wrap: wrap;
}
.hero-stat {
  text-align: center; background: rgba(255,255,255,0.1); padding: 16px 28px;
  border-radius: 12px; border: 1px solid rgba(255,255,255,0.15); min-width: 150px;
}
.hero-stat-num { font-size: 2em; font-weight: 800; color: var(--color-aws-orange-original); }
.hero-stat-label { font-size: 0.75em; opacity: 0.85; margin-top: 4px; }

/* ===== Key Takeaways ===== */
.key-takeaways {
  background: linear-gradient(135deg, #FFF7ED 0%, #FFFBEB 100%);
  border: 2px solid #FDBA74; border-radius: var(--radius-lg);
  padding: 30px; margin: -30px 30px 40px; position: relative; z-index: 10;
}
.key-takeaways h2 {
  font-size: 1.3em; color: var(--color-aws-dark); margin-bottom: 20px;
  display: flex; align-items: center; gap: 10px;
}
.takeaway-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 16px; }
.takeaway-item {
  display: flex; align-items: flex-start; gap: 12px; background: white;
  padding: 16px; border-radius: var(--radius-md); border-left: 4px solid var(--color-aws-orange-original);
}
.takeaway-num {
  background: var(--color-aws-orange-original); color: white; width: 32px; height: 32px;
  border-radius: 50%; display: flex; align-items: center; justify-content: center;
  font-weight: 700; font-size: 0.85em; flex-shrink: 0;
}
.takeaway-text { font-size: 0.92em; line-height: 1.6; }

/* ===== Section ===== */
.section { padding: 40px 30px; border-bottom: 1px solid var(--color-border-light); }
.section:last-child { border-bottom: none; }
.section-label {
  display: inline-block; background: linear-gradient(135deg, var(--color-aws-dark), #37475A);
  color: var(--color-aws-orange-original); padding: 6px 18px; border-radius: 20px;
  font-size: 0.75em; font-weight: 600; letter-spacing: 0.5px; margin-bottom: 12px;
}
.section h2 {
  font-size: 1.5em; color: var(--color-aws-dark); margin-bottom: 20px;
  padding-bottom: 10px; border-bottom: 3px solid var(--color-aws-orange-original); display: inline-block;
}
.section h3 { font-size: 1.15em; color: var(--color-aws-dark); margin: 24px 0 12px; }
.section p { margin-bottom: 16px; line-height: 1.8; }

/* ===== SVG Container ===== */
.svg-container { margin: 30px 0; text-align: center; overflow-x: auto; }
.svg-container svg { max-width: 100%; height: auto; }

/* ===== Analogy Section ===== */
.analogy-intro {
  background: linear-gradient(135deg, #EEF2FF 0%, #F0F9FF 100%);
  border: 2px solid #818CF8; border-radius: var(--radius-lg);
  padding: 30px; margin-bottom: 30px; text-align: center;
}
.analogy-intro .analogy-icon { font-size: 3em; margin-bottom: 12px; }
.analogy-intro h3 { font-size: 1.3em; color: #4338CA; margin-bottom: 10px; }

/* ===== Feature Cards ===== */
.feature-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; margin: 24px 0; }
.feature-card {
  background: var(--color-bg-white); border: 2px solid var(--color-border-light);
  border-radius: var(--radius-lg); padding: 28px; transition: all var(--transition-base);
}
.feature-card:hover { border-color: var(--color-aws-orange-original); box-shadow: var(--shadow-md); transform: translateY(-2px); }
.feature-card-icon {
  width: 52px; height: 52px; border-radius: 12px; display: flex;
  align-items: center; justify-content: center; font-size: 1.5em; margin-bottom: 16px;
}
.feature-card h3 { font-size: 1.05em; color: var(--color-aws-dark); margin-bottom: 10px; }
.feature-card p { font-size: 0.9em; color: var(--color-text-secondary); line-height: 1.7; margin-bottom: 0; }
.icon-blue { background: #EEF2FF; }
.icon-green { background: #ECFDF5; }
.icon-orange { background: #FFF7ED; }
.icon-purple { background: #F5F3FF; }
.icon-red { background: #FEF2F2; }
.icon-teal { background: #F0FDFA; }

/* ===== Code Tabs ===== */
.code-tabs { margin: 24px 0; border-radius: var(--radius-md); overflow: hidden; border: 1px solid var(--color-border-light); }
.tab-buttons { display: flex; background: var(--color-aws-dark); }
.tab-btn {
  background: none; border: none; color: rgba(255,255,255,0.7); padding: 14px 24px;
  font-size: 0.85em; font-weight: 600; cursor: pointer; transition: all var(--transition-base);
  border-bottom: 3px solid transparent; font-family: inherit;
}
.tab-btn:hover { color: white; background: rgba(255,255,255,0.1); }
.tab-btn.active { color: var(--color-aws-orange-original); border-bottom-color: var(--color-aws-orange-original); background: rgba(255,153,0,0.1); }
.tab-content { display: none; background: #1E293B; padding: 24px; overflow-x: auto; }
.tab-content.active { display: block; }
.tab-content pre { color: #E2E8F0; font-family: 'Courier New', monospace; font-size: 0.82em; line-height: 1.6; white-space: pre; margin: 0; }
.tab-content .comment { color: #6B7280; }
.tab-content .keyword { color: #F59E0B; }
.tab-content .string { color: #34D399; }
.tab-content .prop { color: #60A5FA; }

/* ===== Practice Grid ===== */
.practice-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; margin: 24px 0; }
.practice-card { border-radius: var(--radius-lg); padding: 28px; }
.practice-good { background: linear-gradient(135deg, #ECFDF5 0%, #F0FDF4 100%); border: 2px solid #34D399; }
.practice-bad { background: linear-gradient(135deg, #FEF2F2 0%, #FFF1F2 100%); border: 2px solid #F87171; }
.practice-card h3 { font-size: 1.1em; margin-bottom: 16px; display: flex; align-items: center; gap: 8px; }
.practice-good h3 { color: #047857; }
.practice-bad h3 { color: #B91C1C; }
.practice-item { display: flex; align-items: flex-start; gap: 10px; margin-bottom: 12px; font-size: 0.9em; line-height: 1.6; }

/* ===== Trouble Card ===== */
.trouble-card {
  background: var(--color-bg-white); border: 1px solid var(--color-border-light);
  border-radius: var(--radius-md); padding: 24px; margin-bottom: 16px; border-left: 5px solid var(--color-error);
}
.trouble-card h4 { color: var(--color-error); font-size: 1em; margin-bottom: 10px; display: flex; align-items: center; gap: 8px; }
.trouble-solution {
  background: #F0FDF4; border-radius: var(--radius-sm); padding: 14px; margin-top: 10px;
  border-left: 4px solid var(--color-success); font-size: 0.9em;
}
.trouble-solution strong { color: #047857; }

/* ===== Exam Box ===== */
.exam-box {
  background: linear-gradient(135deg, #FFF7ED, #FFFBEB); border: 2px solid var(--color-aws-orange-original);
  border-radius: var(--radius-lg); padding: 30px; margin: 24px 0;
}
.exam-box h3 { color: var(--color-aws-dark); font-size: 1.15em; margin-bottom: 16px; display: flex; align-items: center; gap: 10px; }
.exam-item {
  display: flex; align-items: flex-start; gap: 12px; margin-bottom: 14px;
  padding: 12px; background: white; border-radius: var(--radius-sm); font-size: 0.9em; line-height: 1.6;
}
.exam-badge {
  background: var(--color-aws-dark); color: var(--color-aws-orange-original);
  padding: 3px 10px; border-radius: 12px; font-size: 0.75em; font-weight: 700;
  white-space: nowrap; flex-shrink: 0;
}

/* ===== FAQ ===== */
.faq-item { border: 1px solid var(--color-border-light); border-radius: var(--radius-md); margin-bottom: 12px; overflow: hidden; }
.faq-question {
  width: 100%; background: var(--color-bg-white); border: none; padding: 20px 24px;
  font-size: 0.95em; font-weight: 600; color: var(--color-aws-dark); cursor: pointer;
  display: flex; justify-content: space-between; align-items: center; text-align: left;
  transition: background var(--transition-base); font-family: inherit;
}
.faq-question:hover { background: var(--color-bg-light); }
.faq-question .arrow { font-size: 1.2em; transition: transform var(--transition-base); flex-shrink: 0; margin-left: 16px; }
.faq-item.open .faq-question .arrow { transform: rotate(180deg); }
.faq-answer { display: none; padding: 0 24px 20px; font-size: 0.9em; line-height: 1.8; color: var(--color-text-secondary); }
.faq-item.open .faq-answer { display: block; }

/* ===== Cheat Sheet ===== */
.cheat-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 16px; margin: 20px 0; }
.cheat-item { background: var(--color-bg-light); border-radius: var(--radius-md); padding: 20px; border-left: 4px solid var(--color-info); }
.cheat-item dt { font-weight: 700; color: var(--color-aws-dark); font-size: 0.92em; margin-bottom: 6px; }
.cheat-item dd { font-size: 0.85em; color: var(--color-text-secondary); line-height: 1.6; }

/* ===== Callout ===== */
.callout { border-radius: var(--radius-md); padding: 20px 24px; margin: 20px 0; display: flex; align-items: flex-start; gap: 14px; font-size: 0.9em; line-height: 1.7; }
.callout-info { background: #EFF6FF; border: 1px solid #93C5FD; }
.callout-warning { background: #FFFBEB; border: 1px solid #FCD34D; }
.callout-icon { font-size: 1.3em; flex-shrink: 0; }

/* ===== TOC ===== */
.toc { background: var(--color-bg-light); border: 1px solid var(--color-border-light); border-radius: var(--radius-md); padding: 24px 30px; margin: 20px 30px 30px; }
.toc h2 { font-size: 1.1em; color: var(--color-aws-dark); margin-bottom: 14px; border: none; padding: 0; }
.toc-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 8px 24px; }
.toc-grid a {
  color: var(--color-info); text-decoration: none; font-size: 0.88em; padding: 6px 0;
  display: flex; align-items: center; gap: 8px; transition: color var(--transition-base);
}
.toc-grid a:hover { color: var(--color-aws-orange); }
.toc-num {
  background: var(--color-aws-dark); color: var(--color-aws-orange-original);
  width: 26px; height: 26px; border-radius: 50%; display: flex; align-items: center;
  justify-content: center; font-size: 0.7em; font-weight: 700; flex-shrink: 0;
}

/* ===== Comparison Table (visual) ===== */
.comparison-visual { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; margin: 24px 0; }
.comparison-col { border-radius: var(--radius-lg); padding: 28px; text-align: center; }
.comparison-col h4 { font-size: 1.05em; margin-bottom: 8px; }
.comparison-col p { font-size: 0.85em; line-height: 1.6; }
.comparison-col .comp-icon { font-size: 2.5em; margin-bottom: 12px; }
.comp-left { background: #EEF2FF; border: 2px solid #818CF8; }
.comp-right { background: #FFF7ED; border: 2px solid #FDBA74; }

/* ===== Glossary ===== */
.glossary-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 14px; margin: 20px 0; }
.glossary-item { display: flex; gap: 12px; padding: 14px; background: var(--color-bg-light); border-radius: var(--radius-sm); align-items: flex-start; }
.glossary-term { font-weight: 700; color: var(--color-aws-dark); font-size: 0.88em; min-width: 130px; flex-shrink: 0; }
.glossary-def { font-size: 0.85em; color: var(--color-text-secondary); line-height: 1.5; }

/* ===== Use Cases ===== */
.usecase-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; margin: 24px 0; }
.usecase-card {
  background: linear-gradient(145deg, #F8FAFC, #F0F9FF); border: 2px solid #CBD5E1;
  border-radius: var(--radius-lg); padding: 28px; transition: all var(--transition-base);
}
.usecase-card:hover { border-color: var(--color-info); box-shadow: var(--shadow-md); }
.usecase-card h4 { font-size: 1.02em; color: var(--color-aws-dark); margin-bottom: 10px; display: flex; align-items: center; gap: 10px; }
.usecase-card p { font-size: 0.88em; color: var(--color-text-secondary); line-height: 1.7; margin: 0; }

/* ===== Scroll Top ===== */
.scroll-top {
  position: fixed; bottom: 30px; right: 30px; width: 50px; height: 50px;
  background: var(--color-aws-orange-original); color: white; border: none;
  border-radius: 50%; font-size: 1.3em; cursor: pointer; z-index: 1000;
  display: none; align-items: center; justify-content: center;
  box-shadow: 0 4px 12px rgba(255,153,0,0.4); transition: all var(--transition-base);
}
.scroll-top:hover { background: var(--color-aws-orange-hover); transform: translateY(-3px); }
.scroll-top.visible { display: flex; }

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .takeaway-grid, .feature-grid, .practice-grid, .usecase-grid,
  .cheat-grid, .glossary-grid, .comparison-visual, .toc-grid { grid-template-columns: 1fr; }
  .hero { padding: 40px 20px; }
  .section { padding: 30px 20px; }
  .key-takeaways { margin: -20px 15px 30px; }
  .toc { margin: 15px 15px 20px; }
  .hero-stats { gap: 16px; }
  .hero-stat { min-width: 120px; padding: 12px 16px; }
}