/* =========================================================
   Design tokens
   ========================================================= */
:root {
  --bg: #0f1117;
  --bg-elev: #161923;
  --bg-elev-2: #1c2030;
  --border: #262b3a;
  --text: #e4e6ec;
  --text-dim: #9aa0b4;
  --accent: #5eead4;
  --accent-dim: #2dd4bf;
  --accent-soft: rgba(94, 234, 212, 0.12);
  --accent-glow: rgba(94, 234, 212, 0.35);
  --warn: #fbbf24;
  --code-bg: #0b0d13;
  --code-text: #d5dae6;
  --shadow: 0 12px 32px rgba(0, 0, 0, 0.35);
  --radius: 10px;
  --sidebar-w: 300px;
  --content-max: 1100px;
  color-scheme: dark;
}

:root[data-theme="light"] {
  --bg: #f4f5f9;
  --bg-elev: #ffffff;
  --bg-elev-2: #eceef5;
  --border: #d8dbe6;
  --text: #171a24;
  --text-dim: #5c6278;
  --accent: #0d9488;
  --accent-dim: #0f766e;
  --accent-soft: rgba(13, 148, 136, 0.12);
  --accent-glow: rgba(13, 148, 136, 0.25);
  --warn: #b45309;
  --code-bg: #f7f8fc;
  --code-text: #2a2f3f;
  --shadow: 0 12px 32px rgba(25, 35, 70, 0.08);
  color-scheme: light;
}

/* Accent presets (dark) */
:root[data-accent="violet"] { --accent: #c4b5fd; --accent-dim: #a78bfa; --accent-soft: rgba(167, 139, 250, 0.14); --accent-glow: rgba(167, 139, 250, 0.35); }
:root[data-accent="amber"]  { --accent: #fcd34d; --accent-dim: #f59e0b; --accent-soft: rgba(245, 158, 11, 0.14);  --accent-glow: rgba(245, 158, 11, 0.35); }
:root[data-accent="rose"]   { --accent: #fda4af; --accent-dim: #fb7185; --accent-soft: rgba(251, 113, 133, 0.14); --accent-glow: rgba(251, 113, 133, 0.35); }
:root[data-accent="blue"]   { --accent: #93c5fd; --accent-dim: #60a5fa; --accent-soft: rgba(96, 165, 250, 0.14);  --accent-glow: rgba(96, 165, 250, 0.35); }

/* Accent presets (light) */
:root[data-theme="light"][data-accent="violet"] { --accent: #6d28d9; --accent-dim: #5b21b6; --accent-soft: rgba(109, 40, 217, 0.12); --accent-glow: rgba(109, 40, 217, 0.25); }
:root[data-theme="light"][data-accent="amber"]  { --accent: #b45309; --accent-dim: #92400e; --accent-soft: rgba(180, 83, 9, 0.12);    --accent-glow: rgba(180, 83, 9, 0.25); }
:root[data-theme="light"][data-accent="rose"]   { --accent: #be123c; --accent-dim: #9f1239; --accent-soft: rgba(190, 18, 60, 0.12);   --accent-glow: rgba(190, 18, 60, 0.25); }
:root[data-theme="light"][data-accent="blue"]   { --accent: #1d4ed8; --accent-dim: #1e40af; --accent-soft: rgba(29, 78, 216, 0.12);   --accent-glow: rgba(29, 78, 216, 0.25); }

/* =========================================================
   Base
   ========================================================= */
* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
  display: grid;
  grid-template-columns: var(--sidebar-w) minmax(0, 1fr);
  min-height: 100vh;
  transition: background 0.3s ease, color 0.3s ease;
}

/* ambient glow behind the content */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  background:
    radial-gradient(900px 420px at 75% -12%, var(--accent-soft), transparent 65%),
    radial-gradient(600px 300px at 10% 110%, var(--accent-soft), transparent 70%);
  opacity: 0.9;
  transition: background 0.4s ease;
}

:focus-visible {
  outline: 2px solid var(--accent-dim);
  outline-offset: 2px;
  border-radius: 4px;
}

::selection { background: var(--accent-soft); color: var(--text); }

/* =========================================================
   Reading progress + fixed widgets
   ========================================================= */
.read-progress {
  position: fixed;
  top: 0;
  left: 0;
  height: 3px;
  width: 0%;
  background: linear-gradient(90deg, var(--accent-dim), var(--accent));
  box-shadow: 0 0 12px var(--accent-glow);
  z-index: 60;
  transition: width 0.1s linear;
}

.to-top {
  position: fixed;
  right: 22px;
  bottom: 22px;
  width: 42px;
  height: 42px;
  border-radius: 50%;
  border: 1px solid var(--border);
  background: var(--bg-elev-2);
  color: var(--accent);
  font-size: 1.1rem;
  cursor: pointer;
  z-index: 45;
  box-shadow: var(--shadow);
  opacity: 0;
  transform: translateY(12px);
  pointer-events: none;
  transition: opacity 0.25s ease, transform 0.25s ease, border-color 0.15s, box-shadow 0.15s;
}

.to-top.show { opacity: 1; transform: none; pointer-events: auto; }

.to-top:hover { border-color: var(--accent-dim); box-shadow: 0 0 0 4px var(--accent-soft), var(--shadow); }

/* =========================================================
   Sidebar
   ========================================================= */
.sidebar {
  position: sticky;
  top: 0;
  align-self: start;
  width: var(--sidebar-w);
  height: 100vh;
  background: var(--bg-elev);
  border-right: 1px solid var(--border);
  padding: 22px 18px;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 16px;
  z-index: 20;
  transition: background 0.3s ease, border-color 0.3s ease;
}

.sidebar-brand {
  font-weight: 700;
  font-size: 1.05rem;
  display: flex;
  align-items: center;
  gap: 9px;
  letter-spacing: 0.2px;
}

.sidebar-brand .dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 12px var(--accent-glow);
  flex-shrink: 0;
  animation: breathe 3s ease-in-out infinite;
}

@keyframes breathe {
  0%, 100% { box-shadow: 0 0 6px var(--accent-glow); }
  50%      { box-shadow: 0 0 16px var(--accent-glow), 0 0 2px var(--accent); }
}

/* Appearance / settings panel */
.panel {
  background: var(--bg-elev-2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 12px 14px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.panel-title {
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.7px;
  text-transform: uppercase;
  color: var(--text-dim);
}

.ctl-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
}

.ctl-label {
  font-size: 0.8rem;
  color: var(--text-dim);
}

.seg {
  display: flex;
  gap: 2px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 2px;
}

.seg-btn {
  background: transparent;
  border: none;
  color: var(--text-dim);
  font-size: 0.76rem;
  font-weight: 600;
  letter-spacing: 0.3px;
  padding: 4px 9px;
  min-width: 34px;
  border-radius: 6px;
  cursor: pointer;
  font-family: inherit;
  transition: background 0.15s, color 0.15s;
}

.seg-btn:hover:not(:disabled) { color: var(--text); }

.seg-btn.active {
  background: var(--accent-soft);
  color: var(--accent);
}

.seg-btn:disabled { opacity: 0.35; cursor: default; }

.seg-val {
  align-self: center;
  min-width: 46px;
  text-align: center;
  font-size: 0.74rem;
  font-variant-numeric: tabular-nums;
  color: var(--text);
  background: transparent;
  border: none;
  cursor: pointer;
  padding: 0;
  font-family: inherit;
}

.seg-val:hover { color: var(--accent); }

.swatches { display: flex; gap: 7px; }

.swatch {
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--sw);
  border: 2px solid var(--bg-elev-2);
  box-shadow: 0 0 0 1px var(--border);
  cursor: pointer;
  padding: 0;
  transition: transform 0.15s, box-shadow 0.15s;
}

.swatch:hover { transform: scale(1.12); }

.swatch.active { box-shadow: 0 0 0 2px var(--sw); }

/* Progress */
.progress-wrap {
  background: var(--bg-elev-2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 12px 14px;
}

.progress-label {
  font-size: 0.78rem;
  color: var(--text-dim);
  margin-bottom: 8px;
  display: flex;
  justify-content: space-between;
  gap: 8px;
}

.progress-pct {
  color: var(--accent);
  font-weight: 600;
  font-variant-numeric: tabular-nums;
}

.progress-bar {
  height: 6px;
  border-radius: 4px;
  background: var(--border);
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  width: 0%;
  background: linear-gradient(90deg, var(--accent-dim), var(--accent));
  box-shadow: 0 0 10px var(--accent-glow);
  transition: width 0.4s cubic-bezier(0.2, 0.8, 0.2, 1);
}

.progress-wrap.complete .progress-fill { animation: shimmer 1.6s linear infinite; background-size: 200% 100%;
  background-image: linear-gradient(90deg, var(--accent-dim), var(--accent), var(--accent-dim)); }

@keyframes shimmer { from { background-position: 0% 0; } to { background-position: 200% 0; } }

/* Table of contents */
.toc {
  display: flex;
  flex-direction: column;
  gap: 2px;
  flex: 1;
}

.toc a {
  position: relative;
  color: var(--text-dim);
  text-decoration: none;
  padding: 8px 10px 8px 14px;
  border-radius: 8px;
  font-size: 0.88rem;
  transition: background 0.15s, color 0.15s, transform 0.15s;
}

.toc a::before {
  content: "";
  position: absolute;
  left: 3px;
  top: 50%;
  height: 0;
  width: 3px;
  border-radius: 2px;
  background: var(--accent);
  transform: translateY(-50%);
  transition: height 0.2s ease;
}

.toc a:hover {
  background: var(--bg-elev-2);
  color: var(--text);
  transform: translateX(2px);
}

.toc a.active {
  background: var(--accent-soft);
  color: var(--accent);
  font-weight: 600;
}

.toc a.active::before { height: 60%; }

.reset-btn {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-dim);
  border-radius: 8px;
  padding: 8px 10px;
  font-size: 0.8rem;
  cursor: pointer;
  font-family: inherit;
  transition: border-color 0.15s, color 0.15s, background 0.15s;
}

.reset-btn:hover {
  border-color: var(--accent-dim);
  color: var(--accent);
  background: var(--accent-soft);
}

/* =========================================================
   Main content
   ========================================================= */
.content {
  position: relative;
  z-index: 1;
  padding: 48px clamp(24px, 5vw, 72px) 80px;
  display: flex;
  flex-direction: column;
  align-items: center;
  min-width: 0;
}

.content > * {
  width: 100%;
  max-width: var(--content-max);
}

.page-header { margin-bottom: 8px; }

.page-header h1 {
  font-size: 2.4rem;
  line-height: 1.15;
  margin: 0 0 12px;
  letter-spacing: -0.5px;
  background: linear-gradient(95deg, var(--text) 30%, var(--accent) 100%);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.subtitle {
  color: var(--text-dim);
  font-size: 1.05rem;
  max-width: 680px;
}

.card {
  scroll-margin-top: 24px;
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 28px 32px;
  margin: 28px 0;
  box-shadow: var(--shadow);
  transition: border-color 0.25s ease, box-shadow 0.25s ease, background 0.3s ease;
}

.card:hover {
  border-color: color-mix(in srgb, var(--accent-dim) 45%, var(--border));
}

/* scroll reveal */
.reveal {
  opacity: 0;
  transform: translateY(18px);
  transition: opacity 0.55s ease, transform 0.55s cubic-bezier(0.2, 0.8, 0.2, 1),
              border-color 0.25s ease, box-shadow 0.25s ease, background 0.3s ease;
}

.reveal.in { opacity: 1; transform: none; }

.card h2 {
  position: relative;
  margin-top: 0;
  font-size: 1.45rem;
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border);
}

.card h2 .anchor {
  color: var(--text-dim);
  text-decoration: none;
  font-weight: 400;
  opacity: 0;
  margin-left: -2px;
  transition: opacity 0.15s, color 0.15s;
}

.card h2:hover .anchor, .card h2 .anchor:focus-visible { opacity: 1; }
.card h2 .anchor:hover { color: var(--accent); }

.card h3 {
  font-size: 1.05rem;
  margin: 30px 0 10px;
  padding-left: 12px;
  border-left: 3px solid var(--accent-dim);
  line-height: 1.35;
  color: var(--text);
}

.card h3:first-of-type { margin-top: 22px; }

.badge {
  font-size: 0.7rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.4px;
  background: var(--accent-soft);
  color: var(--accent);
  border: 1px solid color-mix(in srgb, var(--accent-dim) 35%, transparent);
  padding: 4px 10px;
  border-radius: 20px;
}

p { color: var(--text); }

.note {
  font-size: 0.9rem;
  color: var(--text-dim);
  border-left: 3px solid var(--warn);
  padding: 10px 14px 10px 40px;
  background: color-mix(in srgb, var(--warn) 7%, transparent);
  border-radius: 0 8px 8px 0;
  position: relative;
}

.note::before {
  content: "!";
  position: absolute;
  left: 14px;
  top: 11px;
  width: 17px;
  height: 17px;
  border-radius: 50%;
  border: 1.5px solid var(--warn);
  color: var(--warn);
  font-size: 0.7rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  line-height: 1;
}

code {
  font-family: "SF Mono", "Fira Code", Consolas, Menlo, monospace;
  font-size: 0.88em;
  background: var(--bg-elev-2);
  padding: 2px 6px;
  border-radius: 5px;
  color: var(--accent);
}

pre {
  position: relative;
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 42px 18px 16px;
  overflow-x: auto;
  margin: 10px 0 16px;
  transition: border-color 0.2s;
}

pre:hover { border-color: color-mix(in srgb, var(--accent-dim) 40%, var(--border)); }

pre code {
  background: none;
  padding: 0;
  color: var(--code-text);
  font-size: 0.85rem;
  white-space: pre;
}

.lang-chip {
  position: absolute;
  top: 9px;
  left: 12px;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  font-size: 0.66rem;
  font-weight: 600;
  letter-spacing: 0.6px;
  text-transform: uppercase;
  color: var(--text-dim);
  background: var(--bg-elev-2);
  border: 1px solid var(--border);
  padding: 2px 8px;
  border-radius: 5px;
  user-select: none;
}

.copy-btn {
  position: absolute;
  top: 8px;
  right: 8px;
  background: var(--bg-elev-2);
  border: 1px solid var(--border);
  color: var(--text-dim);
  font-size: 0.72rem;
  font-family: inherit;
  padding: 5px 10px;
  border-radius: 6px;
  cursor: pointer;
  opacity: 0;
  transition: opacity 0.15s, color 0.15s, border-color 0.15s, transform 0.1s;
}

pre:hover .copy-btn, .copy-btn:focus-visible { opacity: 1; }

.copy-btn:hover { color: var(--accent); border-color: var(--accent-dim); }
.copy-btn:active { transform: scale(0.96); }

.copy-btn.copied {
  color: var(--accent);
  border-color: var(--accent-dim);
  background: var(--accent-soft);
  opacity: 1;
}

@media (hover: none) { .copy-btn { opacity: 1; } }

/* Tables */
.table {
  width: 100%;
  border-collapse: separate;
  border-spacing: 0;
  border: 1px solid var(--border);
  border-radius: 10px;
  overflow: hidden;
  margin: 14px 0 20px;
  font-size: 0.9rem;
}

.table th, .table td {
  border-bottom: 1px solid var(--border);
  border-right: 1px solid var(--border);
  padding: 10px 12px;
  text-align: left;
  vertical-align: top;
  transition: background 0.15s;
}

.table th:last-child, .table td:last-child { border-right: 0; }
.table tbody tr:last-child td { border-bottom: 0; }

.table th {
  background: var(--bg-elev-2);
  color: var(--text-dim);
  font-weight: 600;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.4px;
}

.table tbody tr:nth-child(even) td { background: color-mix(in srgb, var(--bg-elev-2) 45%, transparent); }
.table tbody tr:hover td { background: var(--accent-soft); }

/* Pipeline diagram */
.diagram {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
  margin: 22px 0 4px;
  font-size: 0.85rem;
}

.diagram-box {
  background: var(--bg-elev-2);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 12px 16px;
  text-align: center;
  flex: 1;
  min-width: 130px;
  transition: border-color 0.2s, box-shadow 0.2s, transform 0.2s;
}

.diagram-box:hover {
  border-color: var(--accent-dim);
  box-shadow: 0 0 0 3px var(--accent-soft);
  transform: translateY(-2px);
}

.diagram-box small { color: var(--text-dim); font-size: 0.72rem; }

.diagram-arrow {
  color: var(--accent);
  font-weight: 700;
  flex-shrink: 0;
  animation: nudge 2.2s ease-in-out infinite;
}

.diagram-arrow:nth-of-type(4) { animation-delay: 0.6s; }

@keyframes nudge {
  0%, 100% { transform: translateX(0); opacity: 0.75; }
  50%      { transform: translateX(4px); opacity: 1; }
}

.plain-list { padding-left: 20px; color: var(--text); }
.plain-list li { margin-bottom: 8px; }
.plain-list li::marker { color: var(--accent); }
ol li::marker { color: var(--accent); font-weight: 600; }

/* =========================================================
   Checklist
   ========================================================= */
.check {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  font-size: 0.9rem;
  color: var(--text-dim);
  background: var(--bg-elev-2);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 10px 14px;
  margin: 6px 0 18px;
  cursor: pointer;
  transition: border-color 0.15s, color 0.15s, background 0.2s, transform 0.15s;
}

.check:hover { border-color: var(--accent-dim); transform: translateX(2px); }

.check input {
  margin-top: 3px;
  accent-color: var(--accent-dim);
  width: 15px;
  height: 15px;
  flex-shrink: 0;
  cursor: pointer;
}

.check:has(input:checked) {
  color: var(--text);
  border-color: var(--accent-dim);
  background: color-mix(in srgb, var(--accent-soft) 70%, var(--bg-elev-2));
}

.check:has(input:checked) code { color: var(--accent); }

/* =========================================================
   Accordion (troubleshooting)
   ========================================================= */
.accordion-item {
  border: 1px solid var(--border);
  border-radius: 10px;
  margin-bottom: 10px;
  overflow: hidden;
  background: var(--bg-elev-2);
  transition: border-color 0.2s;
}

.accordion-item.open { border-color: color-mix(in srgb, var(--accent-dim) 50%, var(--border)); }

.accordion-header {
  width: 100%;
  text-align: left;
  background: none;
  border: none;
  color: var(--text);
  font-family: inherit;
  font-size: 0.92rem;
  font-weight: 600;
  padding: 14px 16px;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 10px;
  transition: background 0.15s;
}

.accordion-header:hover { background: var(--accent-soft); }

.accordion-header .chev {
  color: var(--accent);
  transition: transform 0.25s ease;
  flex-shrink: 0;
}

.accordion-item.open .chev { transform: rotate(90deg); }

.accordion-body {
  display: grid;
  grid-template-rows: 0fr;
  transition: grid-template-rows 0.3s ease;
}

.accordion-item.open .accordion-body { grid-template-rows: 1fr; }

.accordion-inner { min-height: 0; overflow: hidden; padding: 0 16px; }

.accordion-item.open .accordion-inner { padding-bottom: 16px; }

.accordion-body p {
  color: var(--text-dim);
  font-size: 0.88rem;
  margin: 0 0 8px;
}

.accordion-body code { font-size: 0.82em; }

/* =========================================================
   Toast / footer
   ========================================================= */
.toast {
  position: fixed;
  bottom: 24px;
  left: 50%;
  transform: translate(-50%, 20px);
  background: var(--bg-elev-2);
  border: 1px solid var(--accent-dim);
  color: var(--accent);
  padding: 10px 18px;
  border-radius: 8px;
  font-size: 0.85rem;
  box-shadow: var(--shadow);
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.2s ease, transform 0.2s ease;
  z-index: 50;
}

.toast.show { opacity: 1; transform: translate(-50%, 0); }

.page-footer {
  text-align: center;
  color: var(--text-dim);
  font-size: 0.85rem;
  margin-top: 40px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
}

/* =========================================================
   Mobile
   ========================================================= */
.menu-toggle {
  display: none;
  position: fixed;
  top: 14px;
  left: 14px;
  z-index: 30;
  background: color-mix(in srgb, var(--bg-elev-2) 85%, transparent);
  backdrop-filter: blur(8px);
  border: 1px solid var(--border);
  color: var(--text);
  font-size: 1.1rem;
  border-radius: 8px;
  padding: 8px 12px;
  cursor: pointer;
}

.backdrop {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.45);
  z-index: 15;
  opacity: 0;
  transition: opacity 0.2s ease;
}

@media (max-width: 900px) {
  .menu-toggle { display: block; }
  .backdrop { display: block; pointer-events: none; }
  .backdrop.show { opacity: 1; pointer-events: auto; }

  body { display: block; }

  .sidebar {
    position: fixed;
    top: 0;
    left: 0;
    height: 100vh;
    transform: translateX(-100%);
    transition: transform 0.25s ease;
    box-shadow: 4px 0 24px rgba(0, 0, 0, 0.4);
  }

  .sidebar.open { transform: translateX(0); }

  .content { padding: 80px 20px 60px; }
  .card { padding: 20px; }
  .page-header h1 { font-size: 1.9rem; }
  .to-top { right: 16px; bottom: 16px; }
}

/* =========================================================
   Reduced motion
   ========================================================= */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
  .reveal { opacity: 1; transform: none; }
}