:root {
  --bg: #ffffff;
  --bg-secondary: #f8fafc;
  --bg-code: #1e293b;
  --text: #1e293b;
  --text-muted: #64748b;
  --accent: #2563eb;
  --accent-light: #eff6ff;
  --border: #e2e8f0;
  --success: #16a34a;
  --warning: #d97706;
  --danger: #dc2626;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Noto Sans TC',
    'PingFang TC', 'Microsoft JhengHei', sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.75;
  font-size: 16px;
}

/* ── Shared navbar (index page) ── */
.navbar {
  background: var(--bg);
  border-bottom: 1px solid var(--border);
  padding: 0 2rem;
  display: flex;
  align-items: center;
  height: 56px;
  position: sticky;
  top: 0;
  z-index: 100;
  gap: 2rem;
}
.navbar-brand {
  font-weight: 700;
  color: var(--accent);
  text-decoration: none;
  font-size: 1rem;
  white-space: nowrap;
}
.navbar-nav { display: flex; gap: 1.25rem; list-style: none; }
.navbar-nav a { color: var(--text-muted); text-decoration: none; font-size: 0.875rem; transition: color 0.15s; }
.navbar-nav a:hover, .navbar-nav a.active { color: var(--accent); }

/* ── Index page layout ── */
.container { max-width: 860px; margin: 0 auto; padding: 2.5rem 2rem; }
h1 { font-size: 2rem; font-weight: 700; line-height: 1.3; }
h2 { font-size: 1.4rem; font-weight: 600; margin: 2.5rem 0 1rem; padding-bottom: 0.5rem; border-bottom: 2px solid var(--border); }
h3 { font-size: 1.1rem; font-weight: 600; margin: 1.75rem 0 0.6rem; }
p { margin-bottom: 1rem; }
ul, ol { margin: 0.5rem 0 1rem 1.5rem; }
li { margin-bottom: 0.35rem; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

.hero { padding: 2rem 0 1.5rem; border-bottom: 1px solid var(--border); margin-bottom: 0.5rem; }
.hero .subtitle { color: var(--text-muted); margin-top: 0.5rem; font-size: 1.05rem; }

.callout { border-left: 4px solid; padding: 0.9rem 1.25rem; border-radius: 0 6px 6px 0; margin: 1rem 0; font-size: 0.9rem; }
.callout > *:last-child { margin-bottom: 0; }
.callout .callout-title { font-weight: 700; margin-bottom: 0.3rem; font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.05em; }
.callout-info { border-color: var(--accent); background: var(--accent-light); }
.callout-info .callout-title { color: #1d4ed8; }

.course-list { list-style: none; margin: 1rem 0; padding: 0; display: flex; flex-direction: column; gap: 1rem; }
.course-list li { border: 1px solid var(--border); border-radius: 10px; transition: box-shadow 0.2s, border-color 0.2s; }
.course-list li:hover { box-shadow: 0 4px 16px rgba(37,99,235,0.08); border-color: #93c5fd; }
.course-list a { display: block; padding: 1.25rem 1.5rem; text-decoration: none; color: inherit; }
.lesson-num { font-size: 0.75rem; color: var(--text-muted); font-weight: 500; text-transform: uppercase; letter-spacing: 0.05em; margin-bottom: 0.2rem; }
.lesson-title { font-weight: 700; font-size: 1.05rem; color: var(--accent); }
.lesson-desc { font-size: 0.875rem; color: var(--text-muted); margin-top: 0.3rem; line-height: 1.5; }

footer { text-align: center; padding: 2rem; color: var(--text-muted); font-size: 0.825rem; border-top: 1px solid var(--border); margin-top: 3rem; }

/* ════════════════════════════════════════
   PRESENTATION / SLIDE MODE
   ════════════════════════════════════════ */

body.pres {
  height: 100vh;
  overflow: hidden;
  display: grid;
  grid-template-rows: 48px 1fr 52px;
}

/* top bar */
.pres-top {
  background: white;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  padding: 0 1.5rem;
  gap: 1.25rem;
  font-size: 0.875rem;
}
.pres-home {
  color: var(--text-muted);
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 0.35rem;
  transition: color 0.15s;
  white-space: nowrap;
}
.pres-home:hover { color: var(--accent); }
.pres-chapter { color: var(--text); font-weight: 600; }

/* slide deck */
.deck {
  position: relative;
  overflow: hidden;
  background: white;
}

/* individual slide */
.slide {
  position: absolute;
  inset: 0;
  padding: 3rem 5rem;
  display: flex;
  flex-direction: column;
  justify-content: center;
  opacity: 0;
  pointer-events: none;
  transform: translateX(40px);
  transition: opacity 0.22s ease, transform 0.22s ease;
  overflow-y: auto;
}

.slide.active {
  opacity: 1;
  pointer-events: auto;
  transform: translateX(0);
}

/* bottom navigation */
.pres-bottom {
  border-top: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1.5rem;
  background: white;
}

.pres-nav-btns { display: flex; gap: 0.5rem; align-items: center; }

.pres-btn {
  width: 34px; height: 34px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: white;
  cursor: pointer;
  display: flex; align-items: center; justify-content: center;
  font-size: 1rem;
  color: var(--text);
  transition: background 0.15s, border-color 0.15s;
  line-height: 1;
}
.pres-btn:hover:not(:disabled) { background: var(--bg-secondary); border-color: #94a3b8; }
.pres-btn:disabled { opacity: 0.25; cursor: default; }

.pres-counter {
  font-size: 0.8rem;
  color: var(--text-muted);
  min-width: 3rem;
  text-align: center;
}

/* keyboard hint */
.pres-hint {
  font-size: 0.72rem;
  color: var(--text-muted);
  display: flex;
  gap: 0.75rem;
}
.pres-hint kbd {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 3px;
  padding: 0.1em 0.4em;
  font-size: 0.7rem;
}

/* ── Slide typography ── */

.slide h1 {
  font-size: 2.6rem;
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 0.75rem;
}
.slide h2 {
  font-size: 1.75rem;
  font-weight: 700;
  margin-bottom: 1.25rem;
  padding: 0; border: none;
  line-height: 1.3;
}
.slide h3 {
  font-size: 1.15rem;
  font-weight: 600;
  margin: 1.25rem 0 0.6rem;
}

.slide p { margin-bottom: 0.75rem; }
.slide ul, .slide ol { margin: 0.5rem 0 0.75rem 1.5rem; }
.slide li { margin-bottom: 0.5rem; font-size: 1rem; }

.slide-tag {
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--accent);
  font-weight: 700;
  margin-bottom: 0.6rem;
}

/* ── Cover slide ── */
.slide.cover {
  background: linear-gradient(135deg, #eff6ff 0%, #f0fdf4 100%);
  align-items: flex-start;
  justify-content: center;
  padding: 4rem 5rem;
}
.cover-num {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--accent);
  margin-bottom: 1rem;
  letter-spacing: 0.05em;
}
.slide.cover h1 { font-size: 3.25rem; }
.slide.cover .cover-sub {
  font-size: 1.15rem;
  color: var(--text-muted);
  margin-top: 0.75rem;
  max-width: 520px;
}
.slide.cover .cover-next {
  margin-top: 2rem;
  display: inline-block;
  background: var(--accent);
  color: white;
  padding: 0.6rem 1.25rem;
  border-radius: 8px;
  font-weight: 600;
  font-size: 0.9rem;
  text-decoration: none;
}
.slide.cover .cover-next:hover { background: #1d4ed8; text-decoration: none; }

/* ── End slide ── */
.slide.end {
  background: linear-gradient(135deg, #f0fdf4 0%, #eff6ff 100%);
  align-items: center;
  text-align: center;
}
.slide.end h2 { border: none; padding: 0; }
.end-links { display: flex; gap: 1rem; justify-content: center; margin-top: 1.5rem; }
.end-link {
  padding: 0.6rem 1.25rem;
  border-radius: 8px;
  font-weight: 600;
  font-size: 0.9rem;
  text-decoration: none;
}
.end-link.primary { background: var(--accent); color: white; }
.end-link.primary:hover { background: #1d4ed8; text-decoration: none; }
.end-link.secondary { border: 1px solid var(--border); color: var(--text); }
.end-link.secondary:hover { background: var(--bg-secondary); text-decoration: none; }

/* ── Code blocks ── */
.slide code {
  background: #f1f5f9;
  border: 1px solid #cbd5e1;
  padding: 0.15em 0.45em;
  border-radius: 4px;
  font-family: 'Fira Code', 'Cascadia Code', Consolas, monospace;
  font-size: 0.85em;
  color: #be123c;
}
.slide pre {
  background: var(--bg-code);
  border-radius: 8px;
  padding: 1.25rem 1.5rem;
  margin: 0.75rem 0;
  overflow-x: auto;
}
.slide pre code {
  background: none; border: none;
  color: #e2e8f0;
  font-size: 0.9rem;
  padding: 0; line-height: 1.65;
}

/* ── Tables in slides ── */
.slide .table-wrap { overflow-x: auto; margin: 0.75rem 0; }
.slide table { width: 100%; border-collapse: collapse; font-size: 0.875rem; }
.slide th { background: var(--bg-secondary); padding: 0.6rem 0.9rem; text-align: left; border: 1px solid var(--border); font-weight: 600; }
.slide td { padding: 0.6rem 0.9rem; border: 1px solid var(--border); vertical-align: top; }
.slide tr:nth-child(even) td { background: #fafbfc; }

/* ── Callouts in slides ── */
.slide .callout { border-left: 4px solid; padding: 0.8rem 1.1rem; border-radius: 0 6px 6px 0; margin: 0.75rem 0; font-size: 0.9rem; }
.slide .callout > *:last-child { margin-bottom: 0; }
.slide .callout-title { font-weight: 700; margin-bottom: 0.25rem; font-size: 0.75rem; text-transform: uppercase; letter-spacing: 0.05em; }
.slide .callout-info { border-color: var(--accent); background: var(--accent-light); }
.slide .callout-info .callout-title { color: #1d4ed8; }
.slide .callout-tip { border-color: var(--success); background: #f0fdf4; }
.slide .callout-tip .callout-title { color: #15803d; }
.slide .callout-warning { border-color: var(--warning); background: #fffbeb; }
.slide .callout-warning .callout-title { color: #b45309; }

/* ── Two-column layout ── */
.two-col { display: grid; grid-template-columns: 1fr 1fr; gap: 1.5rem; margin-top: 0.5rem; }
.two-col .col { background: var(--bg-secondary); border: 1px solid var(--border); border-radius: 8px; padding: 1.1rem 1.25rem; }
.two-col .col h4 { margin-top: 0; font-size: 0.9rem; color: var(--text-muted); font-weight: 600; margin-bottom: 0.5rem; }

/* ── Tab group in slides ── */
.slide .tab-group { margin: 0.75rem 0; }
.slide .tab-buttons { display: flex; border-bottom: 2px solid var(--border); }
.slide .tab-btn { padding: 0.45rem 1.1rem; border: none; background: none; cursor: pointer; font-size: 0.875rem; color: var(--text-muted); border-bottom: 2px solid transparent; margin-bottom: -2px; transition: color 0.15s, border-color 0.15s; font-family: inherit; }
.slide .tab-btn:hover { color: var(--text); }
.slide .tab-btn.active { color: var(--accent); border-bottom-color: var(--accent); font-weight: 600; }
.slide .tab-content { display: none; padding: 0.75rem 0; }
.slide .tab-content.active { display: block; }

/* ── Badges ── */
.badge { display: inline-block; padding: 0.2em 0.6em; border-radius: 4px; font-size: 0.72rem; font-weight: 600; vertical-align: middle; }
.badge-mac { background: #fce7f3; color: #9d174d; }
.badge-win { background: #dbeafe; color: #1e40af; }
.badge-both { background: #dcfce7; color: #14532d; }

/* ── Step list in slides ── */
.steps { counter-reset: step; list-style: none; margin: 0.75rem 0 0.75rem 0; padding: 0; }
.steps li {
  counter-increment: step;
  display: flex;
  gap: 0.75rem;
  align-items: flex-start;
  margin-bottom: 0.65rem;
}
.steps li::before {
  content: counter(step);
  min-width: 1.6rem; height: 1.6rem;
  background: var(--accent);
  color: white;
  border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  font-weight: 700; font-size: 0.78rem;
  flex-shrink: 0;
}

/* ── Responsive ── */
@media (max-width: 640px) {
  .slide { padding: 1.5rem 1.25rem; }
  .slide.cover { padding: 2rem 1.25rem; }
  .slide.cover h1 { font-size: 2rem; }
  .slide h2 { font-size: 1.35rem; }
  .two-col { grid-template-columns: 1fr; }
  .pres-hint { display: none; }
}