/* ===== DARK THEME (default) ===== */
:root {
  scroll-behavior: smooth;
  --bg: #0f1117;
  --surface: #1a1d27;
  --surface2: #22263a;
  --border: #2e3348;
  --accent: #7c6af7;
  --accent2: #38d9c0;
  --accent3: #f7c948;
  --accent4: #f76c6c;
  --text: #e2e8f0;
  --text-muted: #8892a4;
  --code-bg: #13151f;
  --green: #4ade80;
  --blue: #60a5fa;
  --orange: #fb923c;
  --text-body: #c8d0de;
  --shadow: rgba(0, 0, 0, 0.25);
  --hero-bg-start: #1a1d27;
  --hero-bg-end: #22263a;
  --hero-glow: rgba(124, 106, 247, 0.15);
  --hero-title-start: #fff;
  --hero-title-end: var(--accent);
  --analogy-bg: linear-gradient(
    135deg,
    rgba(124, 106, 247, 0.08),
    rgba(56, 217, 192, 0.05)
  );
  --analogy-border: rgba(124, 106, 247, 0.3);
  --analogy-text: #d0d8e8;
  --code-header-bg: rgba(255, 255, 255, 0.03);
  --code-text: #e2e8f0;
  --row-hover: rgba(124, 106, 247, 0.04);
  --arch-text: #a8b3c4;
  --scrollbar-track: var(--bg);
}

/* ===== LIGHT THEME ===== */
[data-theme="light"] {
  --bg: #f8f7f4;
  --surface: #ffffff;
  --surface2: #f0eeeb;
  --border: #ddd9d1;
  --accent: #6354c7;
  --accent2: #1f9e8c;
  --accent3: #c99b1d;
  --accent4: #d94f4f;
  --text: #2d3142;
  --text-muted: #6b6f80;
  --code-bg: #f4f2ef;
  --green: #22915a;
  --blue: #3b78d0;
  --orange: #d47a1e;
  --text-body: #444857;
  --shadow: rgba(0, 0, 0, 0.08);
  --hero-bg-start: #efedf8;
  --hero-bg-end: #e8f4f2;
  --hero-glow: rgba(99, 84, 199, 0.1);
  --hero-title-start: #2d3142;
  --hero-title-end: #6354c7;
  --analogy-bg: linear-gradient(
    135deg,
    rgba(99, 84, 199, 0.06),
    rgba(31, 158, 140, 0.04)
  );
  --analogy-border: rgba(99, 84, 199, 0.25);
  --analogy-text: #444857;
  --code-header-bg: rgba(0, 0, 0, 0.03);
  --code-text: #374151;
  --row-hover: rgba(99, 84, 199, 0.04);
  --arch-text: #555a6b;
  --scrollbar-track: var(--bg);
}

/* Light theme syntax highlighting overrides */
[data-theme="light"] .kw {
  color: #7c3aed;
}
[data-theme="light"] .str {
  color: #16803c;
}
[data-theme="light"] .num {
  color: #c05621;
}
[data-theme="light"] .fn {
  color: #2563eb;
}
[data-theme="light"] .cmt {
  color: #8b95a5;
  font-style: italic;
}
[data-theme="light"] .var {
  color: #be123c;
}
[data-theme="light"] .obj {
  color: #a16207;
}
[data-theme="light"] .op {
  color: #0891b2;
}
[data-theme="light"] pre code {
  color: var(--code-text);
}
[data-theme="light"] .filetree .dir {
  color: var(--blue);
}
[data-theme="light"] .filetree .file {
  color: var(--green);
}
[data-theme="light"] .filetree .comment {
  color: #8b95a5;
}
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  transition:
    background-color 0.3s ease,
    color 0.3s ease,
    border-color 0.3s ease,
    box-shadow 0.3s ease;
}
body {
  background: var(--bg);
  color: var(--text);
  font-family:
    "Inter",
    system-ui,
    -apple-system,
    sans-serif;
  line-height: 1.7;
  font-size: 16px;
}
/* Sidebar */
.sidebar {
  position: fixed;
  left: 0;
  top: 0;
  bottom: 0;
  width: 260px;
  background: var(--surface);
  border-right: 1px solid var(--border);
  overflow-y: auto;
  padding: 20px 0;
  z-index: 100;
  transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}
body.sidebar-closed .sidebar {
  transform: translateX(-100%);
}

.sidebar-logo {
  padding: 0 20px 20px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 12px;
}
.sidebar-logo h2 {
  font-size: 14px;
  color: var(--accent);
  font-weight: 700;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}
.sidebar-logo p {
  font-size: 11px;
  color: var(--text-muted);
  margin-top: 2px;
}
.nav-section {
  padding: 6px 20px 2px;
  font-size: 10px;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  font-weight: 600;
  margin-top: 8px;
}
.sidebar a {
  display: block;
  padding: 7px 20px;
  font-size: 13px;
  color: var(--text-muted);
  text-decoration: none;
  border-left: 3px solid transparent;
  transition: all 0.2s;
}
.sidebar a:hover,
.sidebar a.active {
  color: var(--accent);
  background: rgba(124, 106, 247, 0.1);
  border-left-color: var(--accent);
}
/* Main */
.main {
  margin: 0 auto;
  margin-left: 260px;
  width: auto;
  padding: 40px 48px 80px;
  transition: margin-left 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}
body.sidebar-closed .main {
  margin-left: 0;
}
/* Hero */
.hero {
  background: linear-gradient(
    135deg,
    var(--hero-bg-start) 0%,
    var(--hero-bg-end) 100%
  );
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 48px;
  margin-bottom: 48px;
  position: relative;
  overflow: hidden;
  box-shadow: 0 4px 24px var(--shadow);
}
.hero::before {
  content: "";
  position: absolute;
  top: -50%;
  right: -20%;
  width: 400px;
  height: 400px;
  background: radial-gradient(circle, var(--hero-glow) 0%, transparent 70%);
  border-radius: 50%;
}
.hero h1 {
  font-size: 36px;
  font-weight: 800;
  background: linear-gradient(
    135deg,
    var(--hero-title-start) 30%,
    var(--hero-title-end) 100%
  );
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  margin-bottom: 12px;
}
.hero p {
  color: var(--text-muted);
  font-size: 17px;
  max-width: 800px;
}
.tag-row {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-top: 20px;
}
.tag {
  padding: 4px 12px;
  border-radius: 20px;
  font-size: 12px;
  font-weight: 600;
  border: 1px solid;
}
.tag-purple {
  color: var(--accent);
  border-color: var(--accent);
  background: rgba(124, 106, 247, 0.1);
}
.tag-teal {
  color: var(--accent2);
  border-color: var(--accent2);
  background: rgba(56, 217, 192, 0.1);
}
.tag-yellow {
  color: var(--accent3);
  border-color: var(--accent3);
  background: rgba(247, 201, 72, 0.1);
}
.tag-red {
  color: var(--accent4);
  border-color: var(--accent4);
  background: rgba(247, 108, 108, 0.1);
}
/* Sections */
section {
  margin-bottom: 60px;
  scroll-margin-top: 24px;
}
h2 {
  font-size: 26px;
  font-weight: 700;
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 2px solid var(--border);
  display: flex;
  align-items: center;
  gap: 10px;
}
h2 .icon {
  font-size: 22px;
}
h3 {
  font-size: 18px;
  font-weight: 600;
  margin: 28px 0 12px;
  color: var(--accent2);
}
h4 {
  font-size: 15px;
  font-weight: 600;
  margin: 20px 0 8px;
  color: var(--accent3);
}
p {
  margin-bottom: 14px;
  color: var(--text-body);
}
/* Concept box */
.concept {
  background: var(--surface);
  border: 1px solid var(--border);
  border-left: 4px solid var(--accent);
  border-radius: 10px;
  padding: 20px 24px;
  margin: 20px 0;
}
.concept.teal {
  border-left-color: var(--accent2);
}
.concept.yellow {
  border-left-color: var(--accent3);
}
.concept.red {
  border-left-color: var(--accent4);
}
.concept.green {
  border-left-color: var(--green);
}
.concept-title {
  font-size: 13px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 8px;
  color: var(--accent);
}
.concept.teal .concept-title {
  color: var(--accent2);
}
.concept.yellow .concept-title {
  color: var(--accent3);
}
.concept.red .concept-title {
  color: var(--accent4);
}
.concept.green .concept-title {
  color: var(--green);
}
/* Analogy box */
.analogy {
  background: var(--analogy-bg);
  border: 1px solid var(--analogy-border);
  border-radius: 10px;
  padding: 20px 24px;
  margin: 20px 0;
  font-style: italic;
  color: var(--analogy-text);
}
.analogy strong {
  color: var(--accent);
  font-style: normal;
}
/* Code */
pre {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  overflow-x: auto;
  margin: 20px 0;
  position: relative;
}
.code-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 16px;
  border-bottom: 1px solid var(--border);
  background: var(--code-header-bg);
}
.code-lang {
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent);
}
.code-title {
  font-size: 12px;
  color: var(--text-muted);
}
pre code {
  display: block;
  padding: 20px;
  font-family: "Fira Code", "Cascadia Code", "Consolas", monospace;
  font-size: 13px;
  line-height: 1.7;
  color: var(--code-text);
}
/* Syntax highlighting */
.kw {
  color: #c792ea;
}
.str {
  color: #c3e88d;
}
.num {
  color: #f78c6c;
}
.fn {
  color: #82aaff;
}
.cmt {
  color: #546e7a;
  font-style: italic;
}
.var {
  color: #f07178;
}
.obj {
  color: #ffcb6b;
}
.op {
  color: #89ddff;
}
/* Step flow */
.steps {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin: 20px 0;
}
.step {
  display: flex;
  align-items: flex-start;
  gap: 16px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 16px 20px;
}
.step-num {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent), #5a48d4);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 14px;
  flex-shrink: 0;
}
.step-content h4 {
  margin: 0 0 4px;
  color: var(--text);
}
.step-content p {
  margin: 0;
  font-size: 14px;
}
/* Grid */
.grid-2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin: 20px 0;
}
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 20px;
  transition: border-color 0.2s;
}
.card:hover {
  border-color: var(--accent);
}
.card-icon {
  font-size: 24px;
  margin-bottom: 8px;
}
.card h4 {
  color: var(--text);
  margin: 0 0 8px;
  font-size: 15px;
}
.card p {
  font-size: 13px;
  margin: 0;
}
/* Table */
table {
  width: 100%;
  border-collapse: collapse;
  margin: 20px 0;
  font-size: 14px;
}
th {
  background: var(--surface2);
  padding: 10px 16px;
  text-align: left;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-muted);
  border-bottom: 2px solid var(--border);
}
td {
  padding: 10px 16px;
  border-bottom: 1px solid var(--border);
  color: var(--text-body);
  vertical-align: top;
}
tr:hover td {
  background: var(--row-hover);
}
/* Architecture diagram */
.arch {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 24px;
  font-family: monospace;
  font-size: 13px;
  color: var(--arch-text);
  overflow-x: auto;
  white-space: pre;
  line-height: 1.6;
  margin: 20px 0;
}
/* File tree */
.filetree {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 16px 20px;
  font-family: monospace;
  font-size: 13px;
  color: var(--arch-text);
  line-height: 1.8;
  margin: 20px 0;
}
.filetree .dir {
  color: var(--blue);
}
.filetree .file {
  color: var(--green);
}
.filetree .comment {
  color: #546e7a;
}
/* Divider */
.divider {
  height: 1px;
  background: var(--border);
  margin: 40px 0;
}
/* Badge */
.badge {
  display: inline-block;
  padding: 2px 8px;
  border-radius: 4px;
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  background: rgba(124, 106, 247, 0.2);
  color: var(--accent);
  margin-left: 8px;
}
.badge.new {
  background: rgba(74, 222, 128, 0.2);
  color: var(--green);
}
.badge.hot {
  background: rgba(251, 146, 60, 0.2);
  color: var(--orange);
}
/* Responsive */
@media (max-width: 900px) {
  .sidebar {
    transform: translateX(-100%);
    width: 260px;
    box-shadow: 2px 0 12px var(--shadow);
  }
  body.sidebar-open .sidebar {
    transform: translateX(0);
  }
  body.sidebar-closed .sidebar {
    transform: translateX(-100%);
  }
  .main {
    margin-left: 0;
    padding: 24px;
    width: 100%;
    transition: opacity 0.3s;
  }
  body.sidebar-open .main {
    opacity: 0.5;
    pointer-events: none;
  }
  .grid-2 {
    grid-template-columns: 1fr;
  }
}

/* Floating Action Button for Sidebar */
.fab-menu {
  position: fixed;
  bottom: 24px;
  right: 24px;
  width: 56px;
  height: 56px;
  border-radius: 50%;
  background: var(--accent);
  color: white;
  border: none;
  box-shadow: 0 4px 16px var(--shadow);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  z-index: 1000;
  transition:
    transform 0.2s cubic-bezier(0.4, 0, 0.2, 1),
    background 0.2s;
}
.fab-menu:hover {
  transform: scale(1.08);
}
.fab-menu:active {
  transform: scale(0.95);
}
.fab-menu svg {
  width: 24px;
  height: 24px;
  stroke: white;
}

/* Scrollbar */
::-webkit-scrollbar {
  width: 6px;
  height: 6px;
}
::-webkit-scrollbar-track {
  background: var(--scrollbar-track);
}
::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 3px;
}
::-webkit-scrollbar-thumb:hover {
  background: var(--accent);
}

/* Theme toggle button */
.theme-toggle {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 20px;
  margin: 0 0 8px;
  cursor: pointer;
  background: transparent;
  border: none;
  color: var(--text-muted);
  font-size: 13px;
  font-family: inherit;
  width: 100%;
  text-align: left;
  transition:
    color 0.2s,
    background 0.2s;
  border-radius: 6px;
}
.theme-toggle:hover {
  color: var(--accent);
  background: var(--row-hover);
}
.theme-toggle .toggle-icon {
  font-size: 18px;
  width: 24px;
  text-align: center;
  transition: transform 0.4s ease;
}
.theme-toggle:hover .toggle-icon {
  transform: rotate(30deg);
}
.theme-toggle .toggle-label {
  font-weight: 600;
  letter-spacing: 0.02em;
}

/* Light mode surface shadow for depth */
[data-theme="light"] .card,
[data-theme="light"] .concept,
[data-theme="light"] .step,
[data-theme="light"] pre {
  box-shadow: 0 1px 4px var(--shadow);
}
[data-theme="light"] .sidebar {
  box-shadow: 2px 0 8px var(--shadow);
}