/* ========================================
   DESIGN SYSTEM & CSS CUSTOM PROPERTIES
   ======================================== */

:root {
  /* Dark Theme (default) */
  --bg-primary: #0d1117;
  --bg-secondary: #161b22;
  --bg-card: #1c2128;
  --bg-card-hover: #21262d;
  --bg-code: #0d1117;
  --bg-nav: rgba(13, 17, 23, 0.85);

  --text-primary: #e6edf3;
  --text-secondary: #8b949e;
  --text-muted: #6e7681;

  --accent: #1793D1;
  --accent-hover: #1fa8e8;
  --accent-glow: rgba(23, 147, 209, 0.15);
  --accent-glow-strong: rgba(23, 147, 209, 0.3);

  --border: #30363d;
  --border-light: #21262d;

  --code-bg: #0d1117;
  --code-header-bg: #161b22;

  --callout-bg: rgba(23, 147, 209, 0.08);
  --callout-border: #1793D1;
  --callout-tip-bg: rgba(46, 160, 67, 0.08);
  --callout-tip-border: #2ea043;

  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 8px 30px rgba(0, 0, 0, 0.5);

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;

  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', monospace;

  --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

[data-theme="light"] {
  --bg-primary: #ffffff;
  --bg-secondary: #f6f8fa;
  --bg-card: #ffffff;
  --bg-card-hover: #f6f8fa;
  --bg-code: #f6f8fa;
  --bg-nav: rgba(255, 255, 255, 0.85);

  --text-primary: #1f2328;
  --text-secondary: #656d76;
  --text-muted: #8b949e;

  --accent: #0969da;
  --accent-hover: #0550ae;
  --accent-glow: rgba(9, 105, 218, 0.1);
  --accent-glow-strong: rgba(9, 105, 218, 0.2);

  --border: #d0d7de;
  --border-light: #e4e8ec;

  --code-bg: #f6f8fa;
  --code-header-bg: #eaeef2;

  --callout-bg: rgba(9, 105, 218, 0.06);
  --callout-border: #0969da;
  --callout-tip-bg: rgba(46, 160, 67, 0.06);
  --callout-tip-border: #1a7f37;

  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.08);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 8px 30px rgba(0, 0, 0, 0.12);
}

/* ========================================
   RESET & BASE
   ======================================== */

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: 80px;
}

body {
  font-family: var(--font-sans);
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
  transition: background var(--transition), color var(--transition);
}

a {
  color: var(--accent);
  text-decoration: none;
  transition: color var(--transition);
}

a:hover {
  color: var(--accent-hover);
}

code {
  font-family: var(--font-mono);
  font-size: 0.875em;
  background: var(--bg-code);
  padding: 0.15em 0.4em;
  border-radius: 4px;
  border: 1px solid var(--border-light);
}

::selection {
  background: var(--accent);
  color: #fff;
}

/* ========================================
   SCROLL PROGRESS BAR
   ======================================== */

.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  height: 3px;
  width: 0%;
  background: linear-gradient(90deg, var(--accent), #58a6ff);
  z-index: 1001;
  transition: width 0.1s linear;
}

/* ========================================
   NAVBAR
   ======================================== */

.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: var(--bg-nav);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border-light);
  transition: background var(--transition), border-color var(--transition);
}

.nav-container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 24px;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--text-primary);
  text-decoration: none;
}

.nav-logo-icon {
  width: 24px;
  height: 24px;
  color: var(--accent);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 8px;
  list-style: none;
}

.nav-link {
  padding: 8px 16px;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  border-radius: var(--radius-sm);
  transition: all var(--transition);
  text-decoration: none;
}

.nav-link:hover {
  color: var(--text-primary);
  background: var(--accent-glow);
}

.nav-link.active {
  color: var(--accent);
  background: var(--accent-glow);
}

/* Theme Toggle */
.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 38px;
  height: 38px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: transparent;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition);
}

.theme-toggle:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-glow);
}

.theme-toggle svg {
  width: 18px;
  height: 18px;
}

[data-theme="dark"] .icon-moon { display: none; }
[data-theme="dark"] .icon-sun { display: block; }
[data-theme="light"] .icon-sun { display: none; }
[data-theme="light"] .icon-moon { display: block; }

/* Mobile Menu */
.mobile-menu-btn {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.mobile-menu-btn span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--text-secondary);
  border-radius: 2px;
  transition: all var(--transition);
}

/* ========================================
   FLOATING SIDE PROGRESS
   ======================================== */

.side-progress {
  position: fixed;
  left: 32px;
  top: 50%;
  transform: translateY(-50%);
  z-index: 100;
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.side-progress-item {
  display: flex;
  align-items: center;
  gap: 12px;
  cursor: pointer;
  transition: all var(--transition);
}

.side-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--border);
  border: 2px solid var(--border);
  transition: all var(--transition);
  flex-shrink: 0;
}

.side-label {
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--text-muted);
  opacity: 0;
  transform: translateX(-8px);
  transition: all var(--transition);
  white-space: nowrap;
}

.side-progress-item:hover .side-label {
  opacity: 1;
  transform: translateX(0);
}

.side-progress-item.active .side-dot {
  background: var(--accent);
  border-color: var(--accent);
  box-shadow: 0 0 8px var(--accent-glow-strong);
}

.side-progress-item.active .side-label {
  opacity: 1;
  transform: translateX(0);
  color: var(--accent);
}

/* ========================================
   HERO SECTION
   ======================================== */

.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
}

.hero-bg {
  position: absolute;
  inset: 0;
  z-index: 0;
}

.hero-grid {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(var(--border-light) 1px, transparent 1px),
    linear-gradient(90deg, var(--border-light) 1px, transparent 1px);
  background-size: 60px 60px;
  opacity: 0.4;
  mask-image: radial-gradient(ellipse 70% 60% at 50% 50%, black 20%, transparent 100%);
  -webkit-mask-image: radial-gradient(ellipse 70% 60% at 50% 50%, black 20%, transparent 100%);
  animation: gridFloat 20s ease-in-out infinite;
}

@keyframes gridFloat {
  0%, 100% { transform: translate(0, 0); }
  25% { transform: translate(-10px, -10px); }
  50% { transform: translate(5px, -5px); }
  75% { transform: translate(-5px, 5px); }
}

.hero-gradient {
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 50% 40% at 50% 50%, var(--accent-glow-strong), transparent),
    radial-gradient(ellipse 80% 60% at 50% 100%, rgba(13, 17, 23, 0.8), transparent);
}

.hero-content {
  position: relative;
  z-index: 1;
  text-align: center;
  padding: 0 24px;
  max-width: 800px;
}

.hero-badge {
  display: inline-block;
  padding: 6px 16px;
  background: var(--accent-glow);
  border: 1px solid var(--accent);
  border-radius: 999px;
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--accent);
  margin-bottom: 28px;
  animation: fadeInUp 0.6s ease-out;
}

.hero-title {
  font-size: clamp(2.2rem, 5vw, 3.8rem);
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.03em;
  margin-bottom: 24px;
  animation: fadeInUp 0.6s ease-out 0.1s both;
}

.text-accent {
  background: linear-gradient(135deg, var(--accent), #58a6ff);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: clamp(1rem, 2vw, 1.15rem);
  color: var(--text-secondary);
  line-height: 1.8;
  margin-bottom: 40px;
  animation: fadeInUp 0.6s ease-out 0.2s both;
}

.hero-btn {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 14px 32px;
  background: var(--accent);
  color: #fff;
  font-weight: 600;
  font-size: 0.95rem;
  border-radius: var(--radius-md);
  text-decoration: none;
  transition: all var(--transition);
  animation: fadeInUp 0.6s ease-out 0.3s both;
  box-shadow: 0 4px 20px rgba(23, 147, 209, 0.3);
}

.hero-btn:hover {
  background: var(--accent-hover);
  color: #fff;
  transform: translateY(-2px);
  box-shadow: 0 6px 24px rgba(23, 147, 209, 0.4);
}

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ========================================
   MAIN CONTENT
   ======================================== */

.main-content {
  max-width: 860px;
  margin: 0 auto;
  padding: 60px 24px 80px;
}

/* ========================================
   GUIDE SECTIONS
   ======================================== */

.guide-section {
  margin-bottom: 48px;
}

.section-header {
  display: flex;
  align-items: center;
  gap: 20px;
  padding: 24px 28px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  cursor: pointer;
  transition: all var(--transition);
  user-select: none;
}

.section-header:hover {
  background: var(--bg-card-hover);
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-glow);
}

.section-number {
  font-size: 1.8rem;
  font-weight: 800;
  color: var(--accent);
  font-family: var(--font-mono);
  line-height: 1;
  flex-shrink: 0;
}

.section-title {
  font-size: 1.35rem;
  font-weight: 700;
  margin-bottom: 4px;
}

.section-desc {
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.collapse-icon {
  width: 24px;
  height: 24px;
  color: var(--text-muted);
  margin-left: auto;
  flex-shrink: 0;
  transition: transform var(--transition);
}

.section-header.collapsed .collapse-icon {
  transform: rotate(-90deg);
}

/* Section Body */
.section-body {
  overflow: hidden;
  max-height: 0;
  opacity: 0;
  transition: max-height 0.5s cubic-bezier(0.4, 0, 0.2, 1),
              opacity 0.3s ease,
              padding 0.3s ease;
  padding: 0 0;
}

.section-body.open {
  max-height: 10000px;
  opacity: 1;
  padding: 20px 0 0;
}

/* ========================================
   CONTENT CARDS
   ======================================== */

.content-card {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-md);
  padding: 28px 32px;
  margin-bottom: 16px;
  transition: all var(--transition);
}

.content-card:hover {
  border-color: var(--border);
  box-shadow: var(--shadow-sm);
}

.card-icon {
  font-size: 1.6rem;
  margin-bottom: 12px;
}

.content-card h3 {
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: 12px;
}

.content-card p {
  color: var(--text-secondary);
  margin-bottom: 16px;
  font-size: 0.95rem;
  line-height: 1.75;
}

.content-card p:last-child {
  margin-bottom: 0;
}

.content-card ol,
.content-card ul {
  color: var(--text-secondary);
  margin-bottom: 16px;
  padding-left: 24px;
}

.content-card li {
  margin-bottom: 6px;
  font-size: 0.95rem;
  line-height: 1.7;
}

/* ========================================
   CODE BLOCKS
   ======================================== */

.code-block {
  border-radius: var(--radius-md);
  border: 1px solid var(--border);
  overflow: hidden;
  margin-bottom: 16px;
  transition: border-color var(--transition);
}

.code-block:hover {
  border-color: var(--accent);
}

.code-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 8px 16px;
  background: var(--code-header-bg);
  border-bottom: 1px solid var(--border);
}

.code-lang {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.copy-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 12px;
  font-family: var(--font-sans);
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--text-muted);
  background: transparent;
  border: 1px solid var(--border);
  border-radius: 4px;
  cursor: pointer;
  transition: all var(--transition);
  position: relative;
}

.copy-btn:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-glow);
}

.copy-btn.copied {
  color: #2ea043;
  border-color: #2ea043;
}

.copy-btn .tooltip {
  position: absolute;
  top: -32px;
  left: 50%;
  transform: translateX(-50%);
  padding: 4px 10px;
  background: #2ea043;
  color: #fff;
  font-size: 0.7rem;
  border-radius: 4px;
  white-space: nowrap;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.2s ease, transform 0.2s ease;
}

.copy-btn.copied .tooltip {
  opacity: 1;
  transform: translateX(-50%) translateY(-4px);
}

.code-block pre {
  padding: 16px 20px;
  background: var(--code-bg);
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.code-block code {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  line-height: 1.7;
  color: var(--text-primary);
  background: none;
  padding: 0;
  border: none;
  white-space: pre;
}

/* ========================================
   INFO CALLOUTS
   ======================================== */

.info-callout {
  padding: 16px 20px;
  background: var(--callout-bg);
  border-left: 3px solid var(--callout-border);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  margin-bottom: 16px;
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.7;
}

.info-callout ul {
  margin-top: 8px;
  margin-bottom: 0;
}

.info-callout--tip {
  background: var(--callout-tip-bg);
  border-left-color: var(--callout-tip-border);
}

/* ========================================
   FADE-IN ANIMATION
   ======================================== */

.fade-in {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.5s ease, transform 0.5s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ========================================
   FOOTER
   ======================================== */

.footer {
  border-top: 1px solid var(--border);
  padding: 48px 24px;
  text-align: center;
  background: var(--bg-secondary);
  transition: background var(--transition), border-color var(--transition);
}

.footer-content {
  max-width: 600px;
  margin: 0 auto;
}

.footer-logo {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  font-size: 1.05rem;
  margin-bottom: 12px;
  color: var(--text-primary);
}

.footer-logo svg {
  color: var(--accent);
}

.footer-text {
  color: var(--text-muted);
  font-size: 0.9rem;
  margin-bottom: 20px;
}

.footer-links {
  display: flex;
  justify-content: center;
  gap: 16px;
}

.footer-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 20px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text-secondary);
  transition: all var(--transition);
  text-decoration: none;
}

.footer-link:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-glow);
}

/* ========================================
   RESPONSIVE
   ======================================== */

@media (max-width: 1100px) {
  .side-progress {
    display: none;
  }
}

@media (max-width: 768px) {
  .nav-links {
    position: fixed;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--bg-nav);
    backdrop-filter: blur(16px);
    flex-direction: column;
    padding: 16px 24px;
    gap: 4px;
    border-bottom: 1px solid var(--border);
    transform: translateY(-100%);
    opacity: 0;
    pointer-events: none;
    transition: transform 0.3s ease, opacity 0.3s ease;
  }

  .nav-links.open {
    transform: translateY(0);
    opacity: 1;
    pointer-events: all;
  }

  .mobile-menu-btn {
    display: flex;
  }

  .mobile-menu-btn.active span:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
  }
  .mobile-menu-btn.active span:nth-child(2) {
    opacity: 0;
  }
  .mobile-menu-btn.active span:nth-child(3) {
    transform: rotate(-45deg) translate(5px, -5px);
  }

  .section-header {
    padding: 18px 20px;
    gap: 14px;
  }

  .section-number {
    font-size: 1.4rem;
  }

  .section-title {
    font-size: 1.1rem;
  }

  .content-card {
    padding: 20px;
  }

  .hero-title {
    font-size: clamp(1.8rem, 5vw, 2.8rem);
  }

  .main-content {
    padding: 40px 16px 60px;
  }
}

@media (max-width: 480px) {
  .nav-container {
    padding: 0 16px;
  }

  .content-card {
    padding: 16px;
  }

  .code-block pre {
    padding: 12px 14px;
  }

  .code-block code {
    font-size: 0.8rem;
  }

  .hero-btn {
    padding: 12px 24px;
    font-size: 0.9rem;
  }
}