/* ============================================================
   How the Bambu Lab A1 Works — design system
   Bambu-themed: dark graphite + Bambu green (#00AE42)
   Zero dependencies. Dark default, light theme via [data-theme].
   ============================================================ */

:root {
  /* Bambu palette — dark (default) */
  --bg:            #131415;
  --bg-soft:       #17191a;
  --panel:         #1a1d1e;
  --panel-2:       #212526;
  --border:        #2a2f30;
  --border-strong: #3a4142;
  --text:          #e8eaea;
  --text-soft:     #b7bfbf;
  --muted:         #8d9797;
  --accent:        #00AE42;   /* Bambu green — surfaces, large marks */
  --accent-text:   #35d475;   /* lightened green — AA text on dark  */
  --accent-soft:   rgba(0, 174, 66, 0.14);
  --accent-border: rgba(0, 174, 66, 0.45);
  --warn:          #e5a53a;
  --warn-soft:     rgba(229, 165, 58, 0.12);
  --danger:        #e05252;
  --code-bg:       #101213;
  --shadow:        0 10px 30px rgba(0, 0, 0, 0.45);

  --sans: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, "SF Mono", SFMono-Regular, Menlo, Consolas, monospace;

  --sidebar-w: 280px;
  --content-w: 760px;
  --radius: 10px;
  --radius-sm: 7px;
}

html[data-theme="light"] {
  --bg:            #f7f8f7;
  --bg-soft:       #f1f3f2;
  --panel:         #ffffff;
  --panel-2:       #eef1ef;
  --border:        #dde2df;
  --border-strong: #c2cac5;
  --text:          #17211b;
  --text-soft:     #3d4a42;
  --muted:         #5f6d64;
  --accent:        #00AE42;
  --accent-text:   #00783a;   /* darkened green — AA text on light */
  --accent-soft:   rgba(0, 174, 66, 0.10);
  --accent-border: rgba(0, 130, 55, 0.45);
  --warn:          #82580c;   /* AA on warn-soft + bg (audit: #9a6a10 was 4.01:1) */
  --warn-soft:     rgba(178, 128, 32, 0.10);
  --danger:        #b83232;
  --code-bg:       #eef1ef;
  --shadow:        0 8px 24px rgba(20, 40, 28, 0.10);
}

* { box-sizing: border-box; }

html { height: 100%; }

body {
  margin: 0;
  min-height: 100%;
  background: var(--bg);
  color: var(--text);
  font-family: var(--sans);
  font-size: 16.5px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

::selection { background: var(--accent); color: #04150a; }

/* ---------- Top bar ---------- */

.topbar {
  position: sticky;
  top: 0;
  z-index: 50;
  display: flex;
  align-items: center;
  gap: 10px;
  height: 58px;
  padding: 0 18px;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--text);
  text-decoration: none;
  font-size: 15.5px;
  letter-spacing: 0.01em;
  min-height: 44px;
}
.brand strong { color: var(--accent-text); font-weight: 700; }
.brand-mark { flex: none; border-radius: 6px; }

.topbar-right { margin-left: auto; display: flex; gap: 8px; }

.icon-btn, .menu-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--panel);
  color: var(--text-soft);
  cursor: pointer;
}
.icon-btn:hover, .menu-btn:hover { color: var(--text); border-color: var(--border-strong); }

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

.menu-btn { display: none; }

/* ---------- Shell layout ---------- */

.shell { display: flex; min-height: calc(100vh - 58px); }

.sidebar {
  flex: none;
  width: var(--sidebar-w);
  padding: 22px 14px 40px;
  border-right: 1px solid var(--border);
  background: var(--bg-soft);
  position: sticky;
  top: 58px;
  align-self: flex-start;
  height: calc(100vh - 58px);
  overflow-y: auto;
}

.side-tier {
  margin: 18px 8px 8px;
  font-size: 11.5px;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--muted);
}
.side-tier:first-child { margin-top: 4px; }

.side-tier-note {
  margin: 18px 10px 6px;
  padding: 10px 11px;
  border-left: 2px solid var(--accent-border);
  color: var(--muted);
  font-size: 12.5px;
  line-height: 1.45;
}

.side-link {
  display: flex;
  align-items: baseline;
  gap: 9px;
  padding: 8px 10px;
  margin: 1px 0;
  border-radius: var(--radius-sm);
  color: var(--text-soft);
  text-decoration: none;
  font-size: 14.5px;
  line-height: 1.35;
  border-left: 2px solid transparent;
  min-height: 44px;
}
.side-link .n {
  font-family: var(--mono);
  font-size: 12px;
  color: var(--muted);
  min-width: 18px;
  text-align: right;
}
.side-link:hover { background: var(--panel-2); color: var(--text); }
.side-link[aria-current="page"] {
  background: var(--accent-soft);
  border-left-color: var(--accent);
  color: var(--text);
}
.side-link[aria-current="page"] .n { color: var(--accent-text); }
.side-done { margin-left: auto; color: var(--accent-text); font-weight: 700; }
.side-link.is-complete .t { color: var(--text); }

.official-resources {
  margin-top: 16px;
  padding-top: 4px;
  border-top: 1px solid var(--border);
}
.official-resources .side-tier { margin-top: 10px; }
.side-link-official { font-size: 13.5px; }
.side-link-official .n {
  color: var(--accent-text);
  min-width: 24px;
}

.trust-legend {
  margin: 22px 8px 0;
  padding-top: 16px;
  border-top: 1px solid var(--border);
}
.trust-legend h2 {
  margin: 0 0 10px;
  color: var(--muted);
  font-size: 11.5px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}
.trust-legend p {
  margin: 9px 0;
  color: var(--muted);
  font-size: 12px;
  line-height: 1.45;
}
.trust-legend .source-label { display: table; margin-bottom: 3px; }

/* ---------- Content ---------- */

.content {
  flex: 1;
  min-width: 0;
  padding: 30px 28px 60px;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.chapter, .pager, .site-footer { width: 100%; max-width: var(--content-w); }

.chapter { padding: 6px 0 10px; }

.tier-chip {
  display: inline-block;
  font-size: 11.5px;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent-text);
  background: var(--accent-soft);
  border: 1px solid var(--accent-border);
  padding: 3px 10px;
  border-radius: 99px;
  margin-bottom: 14px;
}

.chapter h1 {
  font-size: 30px;
  line-height: 1.22;
  margin: 0 0 6px;
  letter-spacing: -0.015em;
}
.chapter h1 .ch-n { color: var(--muted); font-weight: 600; }

.chapter h2 {
  font-size: 20.5px;
  margin: 38px 0 10px;
  letter-spacing: -0.01em;
}
.chapter h2[id] { scroll-margin-top: 122px; }
.chapter h2:focus {
  outline: 3px solid var(--accent-text);
  outline-offset: 6px;
  border-radius: 4px;
}

.chapter p { margin: 14px 0; color: var(--text-soft); }
.chapter p strong, .chapter li strong { color: var(--text); }
.chapter ul, .chapter ol { color: var(--text-soft); padding-left: 24px; }
.chapter li { margin: 6px 0; }

.chapter a { color: var(--accent-text); text-decoration: underline; text-decoration-color: var(--accent-border); text-underline-offset: 2.5px; }
.chapter a:hover { text-decoration-color: var(--accent-text); }

.chapter code, .facts code {
  font-family: var(--mono);
  font-size: 0.86em;
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 5px;
  padding: 1.5px 6px;
  color: var(--text);
}

.chapter hr { border: 0; border-top: 1px solid var(--border); margin: 34px 0; }

.chapter-actions {
  display: flex;
  justify-content: flex-end;
  margin: 8px 0 18px;
}
.complete-btn {
  min-height: 44px;
  padding: 7px 14px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--panel);
  color: var(--text-soft);
  font: inherit;
  font-size: 14px;
  cursor: pointer;
}
.complete-btn[aria-pressed="true"] { color: var(--accent-text); border-color: var(--accent-border); }

.path-context {
  position: sticky;
  top: 68px;
  z-index: 20;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin: -1px 0 18px;
  padding: 9px 12px;
  border: 1px solid var(--accent-border);
  border-radius: var(--radius-sm);
  background: color-mix(in srgb, var(--panel) 94%, transparent);
  box-shadow: 0 5px 16px color-mix(in srgb, var(--bg) 60%, transparent);
  backdrop-filter: blur(8px);
  font-size: 13px;
}
.path-context a { font-weight: 650; }
.path-context span {
  flex: none;
  color: var(--muted);
  font-family: var(--mono);
}

.route-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(min(210px, 100%), 1fr));
  gap: 12px;
  margin: 22px 0;
}
.route-card {
  display: flex;
  flex-direction: column;
  gap: 6px;
  min-height: 132px;
  padding: 17px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--panel);
  color: var(--text);
  text-decoration: none !important;
}
.route-card:hover { border-color: var(--accent-border); }
.route-card strong { color: var(--accent-text); }
.route-card span { color: var(--text-soft); font-size: 14.5px; }
.start-tools { margin: 22px 0; }
.route-steps { padding-left: 26px; }
.route-steps li { padding: 7px 0; }
.route-done { color: var(--accent-text); font-size: 13px; }
.route-preflight h2 { margin: 0 0 8px; font-size: 17px; }
.route-preflight ul { margin-bottom: 0; }
.route-reading-note { font-size: 13.5px; }
.retrieval-list { display: grid; gap: 12px; margin: 22px 0; }
.retrieval-item {
  padding: 15px 17px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--panel);
}
.retrieval-item h2 { margin: 0 0 4px; font-size: 17px; }
.retrieval-item h3 {
  margin: 18px 0 5px;
  color: var(--text);
  font-size: 14px;
}
.retrieval-item p { margin: 7px 0; }
.symptom-checks { margin: 5px 0 12px; }
.symptom-stop {
  padding: 9px 11px;
  border-left: 3px solid var(--warn);
  background: var(--warn-soft);
}
.symptom-source { font-size: 13.5px; }
.glossary-list { margin: 22px 0; }
.glossary-list dt { margin-top: 16px; font-weight: 700; color: var(--text); }
.glossary-list dd { margin: 3px 0 0; color: var(--text-soft); }

/* callouts */
.note, .warn {
  border-radius: var(--radius);
  padding: 13px 16px;
  margin: 18px 0;
  font-size: 15px;
}
.note { background: var(--accent-soft); border: 1px solid var(--accent-border); }
.warn { background: var(--warn-soft); border: 1px solid color-mix(in srgb, var(--warn) 45%, transparent); }
.note > :first-child, .warn > :first-child { margin-top: 0; }
.note > :last-child, .warn > :last-child { margin-bottom: 0; }
.note strong:first-child, .warn strong:first-child { display: inline-block; margin-bottom: 2px; }
.warn strong:first-child { color: var(--warn); }
.note strong:first-child { color: var(--accent-text); }

/* tables */
.chapter table {
  width: 100%;
  border-collapse: collapse;
  margin: 18px 0;
  font-size: 14.5px;
  display: block;
  overflow-x: auto;
}
.chapter th, .chapter td {
  text-align: left;
  padding: 8px 12px;
  border: 1px solid var(--border);
  color: var(--text-soft);
  white-space: nowrap;
}
.chapter td:last-child, .chapter th:last-child { white-space: normal; min-width: 160px; }
.chapter th { background: var(--panel); color: var(--text); font-size: 13px; letter-spacing: 0.03em; }
.chapter tr:nth-child(even) td { background: var(--bg-soft); }

/* spec fact strip */
.facts {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 10px;
  margin: 20px 0;
}
.facts .fact {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 12px 14px;
}
.facts .fact .v { font-size: 19px; font-weight: 700; color: var(--accent-text); font-family: var(--mono); letter-spacing: -0.02em; }
.facts .fact .k { font-size: 12px; color: var(--muted); margin-top: 3px; letter-spacing: 0.04em; text-transform: uppercase; }

/* go deeper row */
.go-deeper {
  margin-top: 40px;
  padding: 16px 18px;
  border: 1px dashed var(--border-strong);
  border-radius: var(--radius);
  font-size: 14.5px;
}
.go-deeper .gd-title {
  font-size: 12px; font-weight: 700; letter-spacing: 0.12em;
  text-transform: uppercase; color: var(--muted); margin-bottom: 8px;
}
.go-deeper a { display: inline-block; margin: 2px 14px 2px 0; }

.source-label {
  display: inline-block;
  padding: 1px 7px;
  border: 1px solid var(--border-strong);
  border-radius: 99px;
  color: var(--text-soft);
  background: var(--panel-2);
  font-family: var(--sans);
  font-size: 10.5px;
  font-weight: 700;
  line-height: 1.6;
  letter-spacing: 0.04em;
  text-decoration: none;
  text-transform: uppercase;
  white-space: nowrap;
}
.source-official { color: var(--accent-text); border-color: var(--accent-border); background: var(--accent-soft); }
.source-community { color: var(--warn); border-color: color-mix(in srgb, var(--warn) 45%, transparent); background: var(--warn-soft); }
.source-illustrative { color: var(--text-soft); border-style: dashed; }

/* ---------- Pager ---------- */

.pager {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 10px 0;
}
.pager-top { border-bottom: 1px solid var(--border); margin-bottom: 14px; }
.pager-bottom { border-top: 1px solid var(--border); margin-top: 26px; }

.pager .progress {
  font-family: var(--mono);
  font-size: 13.5px;
  color: var(--muted);
}
.pager .progress .cur { color: var(--accent-text); font-weight: 700; }

.pg-btn {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  min-height: 44px;
  padding: 8px 18px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--panel);
  color: var(--text);
  font-size: 14.5px;
  font-family: var(--sans);
  cursor: pointer;
  max-width: 42%;
  line-height: 1.3;
  text-decoration: none;
}
.pg-btn:hover:not(:disabled) { border-color: var(--accent-border); color: var(--accent-text); }
.pg-btn:disabled, .pg-btn.is-disabled { opacity: 0.35; cursor: default; }

/* ---------- Playground (sim frame) ---------- */

.playground {
  margin: 26px 0;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--panel);
  overflow: hidden;
  box-shadow: var(--shadow);
}

.pg-head {
  display: flex;
  align-items: center;
  gap: 9px;
  padding: 10px 14px;
  border-bottom: 1px solid var(--border);
  background: var(--panel-2);
}
.pg-dot { width: 8px; height: 8px; border-radius: 50%; background: var(--accent); flex: none; }
.pg-pause {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  margin-left: auto;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--panel);
  color: var(--text-soft);
  font-size: 13px;
  cursor: pointer;
}
.pg-pause:hover { color: var(--accent-text); border-color: var(--accent-border); }
.pg-head .pg-pause + .pg-tag { margin-left: 10px; }
.pg-head h3 { margin: 0; font-size: 13.5px; font-weight: 600; letter-spacing: 0.02em; color: var(--text); }
.pg-head .pg-tag {
  margin-left: auto;
  font-family: var(--mono);
  font-size: 11px;
  color: var(--muted);
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.pg-canvas-wrap { position: relative; background: var(--bg); }
.pg-canvas-wrap canvas { display: block; width: 100%; height: auto; }

.pg-play-overlay {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: color-mix(in srgb, var(--bg) 55%, transparent);
}
.pg-play-overlay button {
  min-height: 44px;
  padding: 10px 22px;
  border-radius: 99px;
  border: 1px solid var(--accent-border);
  background: var(--panel);
  color: var(--accent-text);
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
}

.pg-controls {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 22px;
  padding: 13px 16px 15px;
  border-top: 1px solid var(--border);
  background: var(--panel);
}

.pg-ctl { display: flex; flex-direction: column; gap: 5px; min-width: 150px; flex: 1 1 150px; max-width: 260px; }
.pg-ctl-row { display: flex; align-items: center; gap: 8px; }
.pg-ctl label, .pg-ctl .lbl {
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--muted);
}
.pg-ctl .val { font-family: var(--mono); font-size: 12.5px; color: var(--accent-text); margin-left: auto; }

.pg-ctl input[type="range"] {
  width: 100%;
  height: 44px;
  accent-color: var(--accent);
  cursor: pointer;
  background: transparent;
}

.pg-ctl select {
  background: var(--panel-2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  min-height: 44px;
  padding: 4px 10px;
  font-size: 14px;
  font-family: var(--sans);
  cursor: pointer;
}

.pg-btn-ctl {
  min-height: 44px;
  padding: 6px 16px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--accent-border);
  background: var(--accent-soft);
  color: var(--accent-text);
  font-weight: 600;
  font-size: 13.5px;
  cursor: pointer;
  align-self: flex-start;
}
.pg-btn-ctl:hover { background: var(--accent); color: #05150b; }

/* switch */
.pg-switch { display: inline-flex; align-items: center; gap: 9px; cursor: pointer; min-height: 44px; }
.pg-switch input { position: absolute; opacity: 0; width: 44px; height: 24px; margin: 0; cursor: pointer; }
.pg-switch .track {
  width: 44px; height: 24px; border-radius: 99px;
  background: var(--panel-2); border: 1px solid var(--border-strong);
  position: relative; transition: background 0.15s ease; flex: none;
}
.pg-switch .track::after {
  content: ""; position: absolute; top: 2px; left: 2px;
  width: 18px; height: 18px; border-radius: 50%;
  background: var(--muted); transition: transform 0.15s ease, background 0.15s ease;
}
.pg-switch input:checked + .track { background: var(--accent-soft); border-color: var(--accent); }
.pg-switch input:checked + .track::after { transform: translateX(20px); background: var(--accent); }
.pg-switch input:focus-visible + .track { outline: 2px solid var(--accent-text); outline-offset: 2px; }
.pg-switch .sw-lbl { font-size: 13.5px; color: var(--text-soft); }

.pg-readout {
  font-family: var(--mono);
  font-size: 13px;
  color: var(--text-soft);
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 7px 12px;
  align-self: center;
}
.pg-readout b { color: var(--accent-text); font-weight: 700; }

/* ---------- Footer ---------- */

.site-footer {
  margin-top: 46px;
  padding-top: 18px;
  border-top: 1px solid var(--border);
  font-size: 13px;
  color: var(--muted);
}
.site-footer a { color: var(--text-soft); }

/* ---------- Focus & a11y ---------- */

.visually-hidden {
  position: absolute;
  width: 1px; height: 1px;
  margin: -1px; padding: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

.skip-link {
  position: absolute;
  left: 10px; top: -60px;
  z-index: 200;
  padding: 10px 18px;
  border-radius: var(--radius-sm);
  background: var(--accent);
  color: #04150a;
  font-weight: 700;
  text-decoration: none;
  transition: top 0.15s ease;
}
.skip-link:focus { top: 10px; }

#content:focus { outline: none; }
.chapter-title:focus {
  outline: 3px solid var(--accent-text);
  outline-offset: 6px;
  border-radius: 4px;
}

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

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* ---------- Responsive ---------- */

@media (max-width: 900px) {
  .menu-btn { display: inline-flex; }
  .brand-text { font-size: 14px; }

  .sidebar {
    position: fixed;
    left: 0;
    top: 58px;
    height: calc(100vh - 58px);
    transform: translateX(-100%);
    transition: transform 0.2s ease;
    z-index: 60;
    box-shadow: var(--shadow);
  }
  .sidebar.open { transform: translateX(0); }

  body.drawer-open { overflow: hidden; }

  .backdrop {
    position: fixed;
    inset: 58px 0 0 0;
    background: rgba(0, 0, 0, 0.5);
    z-index: 55;
  }

  .content { padding: 20px 16px 50px; }
  .chapter h1 { font-size: 25px; }
  .pg-controls { gap: 10px 14px; }
  .pg-ctl { max-width: none; }
}

@media (max-width: 480px) {
  body { font-size: 16px; }
  .pg-btn { padding: 8px 13px; }
  .pager { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); }
  .pager .progress { grid-column: 1 / -1; grid-row: 2; text-align: center; }
  .pager .pg-btn { max-width: 100%; }
  .pager .pg-btn:last-child { justify-self: end; text-align: right; }
  .path-context { align-items: flex-start; flex-direction: column; gap: 3px; }
  .retrieval-item { padding: 14px; }
  .source-label { white-space: normal; }
}