:root {
    --slide-transition: 0.5s cubic-bezier(0.4, 0, 0.2, 1);
    --primary-blue: #0078d4;
    --accent-hover: #106ebe;
}

/* Heartbeat Animation */
@keyframes heartbeat {
  0% { transform: scale(1); }
  14% { transform: scale(1.1); }
  28% { transform: scale(1); }
  42% { transform: scale(1.1); }
  56% { transform: scale(1); }
  100% { transform: scale(1); }
}

/* Light Theme (Default) */
body {
    --bg-primary: #ffffff;
    --card-bg: #ffffff;
    --card-secondary: #f5f5f5;
    --text-primary: #000000;
    --text-secondary: #616161;
    --border-color: #e0e0e0;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-hover: 0 4px 16px rgba(0, 0, 0, 0.15);
}

/* Dark Theme */
body[data-theme="dark"] {
    --bg-primary: #1e1e1e;
    --card-bg: #2d2d30;
    --card-secondary: #252526;
    --text-primary: #e0e0e0;
    --text-secondary: #a0a0a0;
    --border-color: #3e3e42;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.4);
    --shadow-hover: 0 4px 16px rgba(0, 0, 0, 0.6);
}

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

html, body {
    height: 100%;
    width: 100%;
    overflow: hidden;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    position: relative;
    line-height: 1.6;
    margin: 0;
    padding: 0;
    display: flex;
    flex-direction: column;
    overflow: hidden;
    transition: background-color 0.3s, color 0.3s;
}

a { color: inherit; text-decoration: none; }
a:hover { opacity: 0.92; }

.header {
  position: sticky;
  top: 0;
  z-index: 10;
  backdrop-filter: blur(10px);
  background: transparent;
  padding: 14px 0;
  border-bottom: 1px solid var(--border-color);
  transition: all 0.3s ease;
}

.brand {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 600;
  color: var(--text-primary);
  font-size: 1rem;
}

.brand img {
  width: 28px;
  height: 28px;
  display: block;
  filter: brightness(100%);
  transition: filter 0.3s ease;
}

body[data-theme="dark"] .brand img {
  filter: brightness(110%);
}

nav {
  display: flex;
  align-items: center;
  gap: 24px;
}

nav a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.95rem;
  transition: color 0.3s ease;
}

nav a:hover {
  color: var(--text-primary);
  opacity: 1;
}

.nav-link {
  border-bottom: 2px solid transparent;
  transition: border-color 0.3s ease, color 0.3s ease;
  color: var(--text-secondary);
}

body[data-theme="dark"] .nav-link {
  color: #e0e0e0 !important;
}

.nav-link:hover {
  color: var(--text-primary);
  border-bottom-color: var(--primary-blue);
}

body[data-theme="dark"] .nav-link:hover {
  color: #ffffff !important;
}

.nav-link.active {
  color: var(--primary-blue);
  border-bottom-color: var(--primary-blue);
}

.container {
    text-align: center;
    z-index: 10;
    padding: 60px 20px;
    max-width: 1400px;
    width: 100%;
    margin: 0 auto;
}

h1 {
    font-size: 2.5rem;
    font-weight: 600;
    margin-bottom: 12px;
    letter-spacing: -0.01em;
    color: var(--text-primary);
}

.subtitle {
    font-size: 1.1rem;
    margin-bottom: 48px;
    color: var(--text-secondary);
    font-weight: 400;
    letter-spacing: 0;
}

/* Header/Footer Wrapper */
.header-wrapper, .top {
  position: sticky;
  top: 0;
  z-index: 10;
  backdrop-filter: blur(10px);
  background: transparent;
  padding: 14px 0;
  border-bottom: 1px solid var(--border-color);
  transition: padding 0.25s ease;
  flex-shrink: 0;
}

.top.scrolled {
  padding: 8px 0;
}

.top.scrolled .nav-pill {
  padding: 7px 12px;
  gap: 10px;
}

.nav-pill {
  width: min(1040px, 100%);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 10px 14px;
  border-radius: 999px;
  border: 1px solid var(--border-color);
  background: rgba(255, 255, 255, 0.70);
  box-shadow: 0 10px 30px rgba(15, 23, 42, 0.10);
  transition: padding 0.25s ease, gap 0.25s ease;
}

body[data-theme="dark"] .nav-pill {
  background: rgba(45, 45, 50, 0.95) !important;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.6) !important;
  border-color: rgba(80, 80, 88, 0.9) !important;
}

/* Theme Toggle Button */
.theme-toggle {
    position: fixed;
    top: 20px;
    right: 20px;
    z-index: 1000;
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    width: 44px;
    height: 44px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: 1.3rem;
    transition: all 0.3s ease;
    box-shadow: var(--shadow);
}

.theme-toggle:hover {
    transform: scale(1.1);
    border-color: var(--primary-blue);
    box-shadow: var(--shadow-hover);
}

/* Content Cards Styling */
.content-card {
    background: var(--card-bg);
    border-radius: 8px;
    padding: 32px;
    border: 1px solid var(--border-color);
    text-align: left;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: var(--shadow);
    display: block;
    color: inherit;
    text-decoration: none;
    cursor: pointer;
  position: relative;
}

/* Launch-style border frame (uses existing theme accent vars) */
.content-card::before {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: 8px;
  padding: 2px;
  background: linear-gradient(var(--card-accent-angle, 45deg), var(--primary-blue), var(--accent-hover));
  pointer-events: none;
  opacity: 0.55;
  transition: opacity 0.3s ease;
  filter: hue-rotate(var(--card-accent-hue, 0deg)) saturate(1.25);

  /* Show gradient only on the border */
  -webkit-mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
  -webkit-mask-composite: xor;
      mask-composite: exclude;
}

body[data-theme="dark"] .content-card::before {
  opacity: 0.45;
}

.content-card[data-section="ai"] { --card-accent-angle: 25deg; --card-accent-hue: 0deg; }
.content-card[data-section="security"] { --card-accent-angle: 110deg; --card-accent-hue: 120deg; }
.content-card[data-section="interactive"] { --card-accent-angle: 200deg; --card-accent-hue: 240deg; }
.content-card[data-section="about"] { --card-accent-angle: 300deg; --card-accent-hue: 300deg; }

.content-card:hover {
    border-color: var(--primary-blue);
    transform: translateY(-3px);
    box-shadow: var(--shadow-hover);
}

.content-card:hover::before {
  opacity: 0.95;
}

.card-icon {
    font-size: 2.5rem;
    margin-bottom: 16px;
    display: flex;
    justify-content: center;
    align-items: center;
    text-align: center;
}

/* Diagram blocks (used by /learn/ai/) */
.diagram {
  display: grid;
  gap: 10px;
  margin-top: 10px;
}

.diagram-row {
  display: grid;
  grid-template-columns: 1fr auto 1fr auto 1fr;
  gap: 10px;
  align-items: center;
}

@media (max-width: 900px) {
  .diagram-row {
    grid-template-columns: 1fr;
  }

  .diagram-arrow {
    display: none;
  }
}

.diagram-box {
  background: var(--card-secondary);
  border: 1px solid var(--border-color);
  border-radius: 10px;
  padding: 12px 14px;
  box-shadow: var(--shadow);
}

.diagram-title {
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 4px;
}

.diagram-sub {
  color: var(--text-secondary);
  font-size: 0.95rem;
}

.diagram-arrow {
  color: var(--text-secondary);
  font-weight: 600;
  text-align: center;
  user-select: none;
}

/* Interactive diagram tour (used by /learn/ai/) */
.diagram-tour {
  margin: 12px 0 18px 0;
  padding: 12px 12px;
  border: 1px solid var(--border-color);
  border-radius: 10px;
  background: var(--card-secondary);
}

.diagram-tour-header {
  display: flex;
  gap: 12px;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
}

.diagram-tour-kicker {
  text-transform: uppercase;
  letter-spacing: 0.1em;
  font-weight: 700;
  font-size: 0.72rem;
  color: var(--primary-blue);
}

.diagram-tour-title {
  font-weight: 700;
  color: var(--text-primary);
  margin-top: 4px;
}

.diagram-tour-controls {
  display: flex;
  align-items: center;
  gap: 10px;
}

.diagram-tour-btn {
  background: var(--card-bg);
  color: var(--text-primary);
  border: 1px solid var(--border-color);
  border-radius: 999px;
  padding: 8px 12px;
  font-weight: 600;
  cursor: pointer;
}

.diagram-tour-btn:hover {
  border-color: var(--primary-blue);
}

.diagram-tour-btn:focus-visible {
  outline: 2px solid var(--primary-blue);
  outline-offset: 2px;
}

.diagram-tour-progress {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

.diagram-tour-body {
  margin-top: 10px;
  color: var(--text-secondary);
  line-height: 1.6;
}

.diagram-tour-hint {
  margin-top: 10px;
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.diagram-box[data-node] {
  cursor: pointer;
  transition: transform 160ms ease, border-color 160ms ease, box-shadow 160ms ease, opacity 160ms ease;
}

.diagram-box[data-node]:hover {
  border-color: var(--primary-blue);
  transform: translateY(-1px);
}

.diagram-box.is-focus {
  border-color: var(--primary-blue);
  box-shadow: var(--shadow-hover);
}

.diagram.is-dimming .diagram-box[data-node] {
  opacity: 0.45;
}

.diagram.is-dimming .diagram-box.is-focus {
  opacity: 1;
}

/* AI lesson helpers (scoped) */
.ai-lesson .lesson-quote {
  margin: 14px 0 10px 0;
  padding: 12px 14px;
  border-radius: 10px;
  border: 1px solid var(--border-color);
  background: var(--card-secondary);
}

.ai-lesson .lesson-quote-title {
  text-transform: uppercase;
  letter-spacing: 0.1em;
  font-weight: 700;
  font-size: 0.72rem;
  color: var(--primary-blue);
}

.ai-lesson .lesson-quote-text {
  margin-top: 6px;
  color: var(--text-primary);
  font-weight: 600;
}

.ai-lesson .lesson-toc {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin: 12px 0 18px 0;
}

.ai-lesson .lesson-toc-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 12px;
  border-radius: 999px;
  border: 1px solid var(--border-color);
  background: var(--card-bg);
  color: var(--text-secondary);
  font-size: 0.92rem;
  text-decoration: none;
}

.ai-lesson .lesson-toc-link:hover {
  border-color: var(--primary-blue);
  color: var(--text-primary);
  opacity: 1;
}

.ai-lesson .lesson-details {
  margin-top: 12px;
  padding: 10px 12px;
  border-radius: 10px;
  border: 1px solid var(--border-color);
  background: var(--card-secondary);
}

.ai-lesson .lesson-details > summary {
  cursor: pointer;
  color: var(--text-primary);
  font-weight: 600;
}

.ai-lesson .lesson-details > summary:hover {
  opacity: 0.92;
}

/* Attention demo (scoped) */
.ai-lesson .attention-demo {
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: 12px 14px;
  background: var(--card-secondary);
}

/* Slide-deck layout (AI basics) */
.ai-deck-shell {
  flex: 1;
  position: relative;
  overflow: hidden;
}

.ai-deck {
  position: absolute;
  inset: 0;
}

.deck-slide {
  position: absolute;
  inset: 0;
  opacity: 0;
  visibility: hidden;
  transition: opacity var(--slide-transition), visibility var(--slide-transition);
  overflow-y: auto;
  overflow-x: hidden;
  padding: 0 0 120px 0;
}

.deck-slide.is-active {
  opacity: 1;
  visibility: visible;
  z-index: 1;
}

.deck-slide::-webkit-scrollbar {
  width: 8px;
}

.deck-slide::-webkit-scrollbar-track {
  background: transparent;
}

.deck-slide::-webkit-scrollbar-thumb {
  background: var(--border-color);
  border-radius: 4px;
}

.deck-slide::-webkit-scrollbar-thumb:hover {
  background: var(--text-secondary);
}

.deck-nav-arrow {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  width: 48px;
  height: 48px;
  border-radius: 999px;
  border: 1px solid var(--border-color);
  background: var(--card-bg);
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  cursor: pointer;
  user-select: none;
  z-index: 20;
  box-shadow: var(--shadow);
}

.deck-nav-arrow:hover {
  border-color: var(--primary-blue);
  color: var(--text-primary);
  box-shadow: var(--shadow-hover);
}

.deck-nav-arrow.disabled {
  opacity: 0.3;
  pointer-events: none;
}

.deck-nav-arrow.left { left: 18px; }
.deck-nav-arrow.right { right: 18px; }

.deck-indicator {
  position: absolute;
  left: 50%;
  transform: translateX(-50%);
  bottom: 18px;
  display: flex;
  gap: 10px;
  z-index: 20;
  padding: 10px 14px;
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: 999px;
  box-shadow: var(--shadow);
}

.deck-dot {
  width: 8px;
  height: 8px;
  border-radius: 999px;
  background: var(--text-secondary);
  opacity: 0.4;
  border: 0;
  cursor: pointer;
}

.deck-dot:hover { opacity: 0.7; }

.deck-dot.active {
  width: 24px;
  opacity: 1;
  background: var(--primary-blue);
}

.deck-progress {
  position: absolute;
  left: 18px;
  bottom: 18px;
  z-index: 20;
  padding: 8px 12px;
  border-radius: 999px;
  border: 1px solid var(--border-color);
  background: var(--card-bg);
  color: var(--text-secondary);
  box-shadow: var(--shadow);
  font-size: 0.9rem;
}

@media (max-width: 768px) {
  .deck-nav-arrow { width: 40px; height: 40px; font-size: 1.25rem; }
  .deck-indicator { bottom: 14px; }
  .deck-progress { display: none; }
}

/* Exercises (AI basics) */
.exercise {
  margin-top: 14px;
  padding: 12px 14px;
  border-radius: 12px;
  border: 1px solid var(--border-color);
  background: var(--card-secondary);
}

.exercise-title {
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 6px;
}

.exercise-question {
  color: var(--text-secondary);
  margin-bottom: 10px;
}

.exercise-options {
  display: grid;
  gap: 10px;
}

.exercise-option {
  text-align: left;
  padding: 10px 12px;
  border-radius: 10px;
  border: 1px solid var(--border-color);
  background: var(--card-bg);
  color: var(--text-primary);
  cursor: pointer;
}

.exercise-option:hover {
  border-color: var(--primary-blue);
}

.exercise-option.is-selected {
  border-color: var(--primary-blue);
  box-shadow: var(--shadow);
}

.exercise-feedback {
  margin-top: 10px;
  color: var(--text-primary);
  font-weight: 600;
}

.exercise-row {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.exercise-input {
  flex: 1;
  min-width: 240px;
  padding: 10px 12px;
  border-radius: 10px;
  border: 1px solid var(--border-color);
  background: var(--card-bg);
  color: var(--text-primary);
}

.exercise-input:focus-visible {
  outline: 2px solid var(--primary-blue);
  outline-offset: 2px;
}

.exercise-action {
  padding: 10px 12px;
  border-radius: 10px;
  border: 1px solid var(--border-color);
  background: var(--card-bg);
  color: var(--text-primary);
  cursor: pointer;
  font-weight: 700;
}

.exercise-action:hover {
  border-color: var(--primary-blue);
}

.exercise-output {
  margin-top: 10px;
  padding: 10px 12px;
  border-radius: 10px;
  border: 1px dashed var(--border-color);
  background: var(--card-bg);
  color: var(--text-secondary);
  word-break: break-word;
}

.ai-lesson .attention-demo-label {
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-secondary);
  font-weight: 700;
  margin-bottom: 8px;
}

.ai-lesson .token-strip {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.ai-lesson .token-chip {
  border: 1px solid var(--border-color);
  background: var(--card-bg);
  color: var(--text-primary);
  border-radius: 999px;
  padding: 8px 10px;
  font-weight: 600;
  cursor: pointer;
}

.ai-lesson .token-chip:hover {
  border-color: var(--primary-blue);
}

.ai-lesson .token-chip:focus-visible {
  outline: 2px solid var(--primary-blue);
  outline-offset: 2px;
}

.ai-lesson .token-chip.is-focus {
  border-color: var(--primary-blue);
  box-shadow: var(--shadow-hover);
}

.ai-lesson .token-chip.attn-1 {
  border-color: var(--primary-blue);
}

.ai-lesson .token-chip.attn-2 {
  border-color: var(--primary-blue);
  box-shadow: var(--shadow);
}

.ai-lesson .token-chip.attn-3 {
  border-color: var(--primary-blue);
  box-shadow: var(--shadow-hover);
}

.ai-lesson .attention-demo-focus {
  font-weight: 700;
  color: var(--text-primary);
}

.ai-lesson .attn-weights {
  display: grid;
  gap: 8px;
}

.ai-lesson .attn-row {
  display: grid;
  grid-template-columns: 120px 1fr 52px;
  gap: 10px;
  align-items: center;
}

@media (max-width: 520px) {
  .ai-lesson .attn-row {
    grid-template-columns: 90px 1fr 46px;
  }
}

.ai-lesson .attn-token {
  color: var(--text-primary);
  font-weight: 600;
}

.ai-lesson .attn-row.is-focus .attn-token {
  color: var(--primary-blue);
}

.ai-lesson .attn-bar {
  position: relative;
  height: 10px;
  border-radius: 999px;
  border: 1px solid var(--border-color);
  background: var(--card-bg);
  overflow: hidden;
}

.ai-lesson .attn-bar::before {
  content: "";
  position: absolute;
  inset: 0;
  width: var(--w, 0%);
  background: var(--primary-blue);
}

.ai-lesson .attn-pct {
  text-align: right;
  color: var(--text-secondary);
  font-variant-numeric: tabular-nums;
}

.card-icon img {
    width: 48px;
    height: 48px;
    display: block;
}

.card-title {
    font-size: 1.3rem;
    font-weight: 600;
    margin-bottom: 20px;
    color: var(--text-primary);
    text-align: center;
    letter-spacing: 0;
}

.card-section {
    margin-bottom: 20px;
}

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

.section-label {
    font-size: 0.75rem;
    color: var(--primary-blue);
    margin-bottom: 8px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
}

.section-text {
    font-size: 0.9375rem;
    line-height: 1.6;
    color: var(--text-secondary);
}

.analogy-box {
    padding: 16px;
    background: var(--card-secondary);
    border-radius: 6px;
    border-left: 3px solid var(--primary-blue);
}

.analogy-box .section-text {
    font-style: italic;
    color: var(--text-secondary);
}

/* Horizontal Scrolling Container */
.horizontal-scroll-container {
    width: 100%;
    flex: 1;
    min-height: 0;
    overflow-x: auto;
    overflow-y: hidden;
    scroll-behavior: smooth;
    scroll-snap-type: x mandatory;
    display: flex;
    align-items: center;
    /* Hide scrollbar */
    -ms-overflow-style: none;
    scrollbar-width: none;
}

.horizontal-scroll-container::-webkit-scrollbar {
    display: none;
}

/* Homepage scroll indicator (dots) */
.scroll-indicator {
  position: fixed;
  left: 50%;
  bottom: clamp(64px, 9vh, 92px);
  transform: translateX(-50%);
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 12px;
  border-radius: 999px;
  border: 1px solid var(--border-color);
  background: var(--card-bg);
  box-shadow: var(--shadow);
  z-index: 5;
  pointer-events: none;
}

.scroll-dot {
  width: 9px;
  height: 9px;
  border-radius: 999px;
  border: 1px solid var(--border-color);
  background: transparent;
  opacity: 0.7;
}

.scroll-dot.active {
  background: var(--primary-blue);
  border-color: var(--primary-blue);
  opacity: 1;
}

.scroll-content {
    display: flex;
    gap: 24px;
    padding: 0 40px;
    max-width: none;
    min-width: min-content;
    height: 100%;
    align-items: center;
}

/* Vertical, full-width page override (used by /learn/ai) */
.ai-page-scroll {
  overflow-x: hidden;
  overflow-y: auto;
  scroll-snap-type: none;
  align-items: stretch;
}

.ai-page-scroll .scroll-content {
  flex-direction: column;
  align-items: stretch;
  justify-content: flex-start;
  height: auto;
  min-width: 0;
  width: 100%;
  padding: 18px 20px;
  gap: 18px;
}

.ai-page {
  width: 100%;
  max-width: none;
  height: auto;
  overflow: visible;
  padding: 0;
  background: transparent;
  border: none;
  box-shadow: none;
}

.content-card {
    flex: 0 0 clamp(320px, 70vw, 600px);
    height: 50vh;
    scroll-snap-align: center;
    scroll-snap-stop: always;
    overflow-y: auto;
}

.content-card::-webkit-scrollbar {
    width: 6px;
}

.content-card::-webkit-scrollbar-track {
    background: transparent;
}

.content-card::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 3px;
}

.content-card::-webkit-scrollbar-thumb:hover {
    background: var(--text-secondary);
}

@media (max-width: 768px) {
    .scroll-content {
        padding: 0 20px;
    }

    .content-card {
        flex: 0 0 clamp(280px, 95vw, 600px);
        height: 80vh;
    }
}

@media (max-width: 768px) {
    h1 {
        font-size: 2rem;
    }

    .subtitle {
        font-size: 0.95rem;
    }

    .content-card {
        padding: 24px;
    }

    .cards-grid {
        grid-template-columns: 1fr;
        gap: 20px;
    }
}

/* Footer */
footer {
  border-top: 1px solid var(--border-color);
  padding: 22px 0;
  color: var(--text-secondary);
  background: var(--bg-primary);
  display: block;
  width: 100%;
  text-align: center;
  font-size: 13px;
  margin: 0;
  flex-shrink: 0;
}

footer .container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 20px;
}

footer p {
  margin: 0;
  color: var(--text-secondary);
}