/* gordma tutorial — light Claude-style theme, cream background */
:root {
  --bg: #F5F1E8;           /* page cream/beige */
  --bg-sidebar: #EFEAE0;   /* slightly deeper cream */
  --surface: #FFFFFF;      /* cards / code */
  --surface-alt: #FAF8F3;
  --ink: #1F1E1C;          /* primary text */
  --ink-soft: #4A453E;     /* body text */
  --muted: #8B857B;        /* meta / captions */
  --line: #E4DDD0;         /* borders */
  --accent: #D97757;       /* Claude terracotta */
  --accent-soft: #FBEDE7;
  --green: #5B8A72;
  --blue: #4A6FA5;
  --gold: #C99A3C;
  --code-bg: #F3EFE6;
  --radius: 10px;
  --maxw: 820px;
  --sidebar-w: 290px;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC',
    'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
  background: var(--bg);
  color: var(--ink-soft);
  line-height: 1.72;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

/* ---------- Layout ---------- */
.layout { display: flex; min-height: 100vh; }

.sidebar {
  width: var(--sidebar-w);
  flex: 0 0 var(--sidebar-w);
  background: var(--bg-sidebar);
  border-right: 1px solid var(--line);
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
  padding: 1.75rem 1.25rem 2.5rem;
}

.content {
  flex: 1 1 auto;
  min-width: 0;
  display: flex;
  justify-content: center;
  padding: 3rem 2.5rem 5rem;
}
.content-inner { width: 100%; max-width: var(--maxw); }

/* ---------- Sidebar nav ---------- */
.brand { display: flex; align-items: center; gap: 0.6rem; margin-bottom: 0.35rem; }
.brand .logo {
  width: 30px; height: 30px; border-radius: 8px;
  background: var(--accent); color: #fff;
  display: grid; place-items: center;
  font-weight: 700; font-size: 1rem;
  box-shadow: 0 2px 6px rgba(217,119,87,0.35);
}
.brand .name { font-weight: 700; color: var(--ink); font-size: 1.05rem; letter-spacing: -0.01em; }
.brand-sub { color: var(--muted); font-size: 0.75rem; margin-bottom: 1.5rem; padding-left: 0.1rem; }

.nav-group { margin-bottom: 1.1rem; }
.nav-group > .nav-title {
  font-size: 0.7rem; text-transform: uppercase; letter-spacing: 0.08em;
  color: var(--muted); font-weight: 700; margin-bottom: 0.5rem; padding-left: 0.6rem;
}
/* part label = link to the part's first page */
.nav a.nav-part {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--ink);
  text-decoration: none;
  padding: 0.4rem 0.65rem;
  margin-bottom: 0.15rem;
  border-left: 2px solid transparent;
}
.nav a.nav-part:hover { background: rgba(217,119,87,0.08); }
.nav a.nav-part.active {
  background: var(--accent-soft);
  color: var(--accent);
}
.nav a.nav-part .caret {
  display: inline-block;
  font-size: 0.95rem;
  color: var(--muted);
  transition: transform 0.18s ease;
  width: 0.7rem;
  text-align: center;
  flex: 0 0 auto;
}
/* collapsible sub-list: hidden by default, revealed when group is open */
.nav .sub {
  overflow: hidden;
  max-height: 0;
  opacity: 0;
  transition: max-height 0.22s ease, opacity 0.18s ease;
}
.nav-group.open .sub { max-height: 30rem; opacity: 1; }
.nav-group.open > a.nav-part .caret { transform: rotate(90deg); color: var(--accent); }
.nav a {
  display: block;
  text-decoration: none;
  color: var(--ink-soft);
  font-size: 0.875rem;
  padding: 0.4rem 0.65rem;
  border-radius: 7px;
  border-left: 2px solid transparent;
  transition: background 0.12s, color 0.12s;
}
.nav a:hover { background: rgba(217,119,87,0.08); color: var(--ink); }
.nav a.active {
  background: var(--accent-soft);
  color: var(--accent);
  font-weight: 600;
}
.nav .sub a {
  font-size: 0.83rem;
  padding: 0.32rem 0.65rem 0.32rem 1.35rem;
  color: var(--ink-soft);
}
.nav .sub a:hover { color: var(--ink); background: rgba(217,119,87,0.06); }
.nav .sub a.active {
  background: var(--accent-soft);
  color: var(--accent);
  font-weight: 600;
}

/* ---------- Typography ---------- */
.kicker {
  display: inline-block;
  font-size: 0.72rem; font-weight: 700; letter-spacing: 0.09em;
  text-transform: uppercase; color: var(--accent);
  background: var(--accent-soft);
  padding: 0.25rem 0.7rem; border-radius: 20px; margin-bottom: 1rem;
}
h1 {
  font-size: 2.15rem; font-weight: 800; color: var(--ink);
  letter-spacing: -0.02em; line-height: 1.18; margin-bottom: 0.6rem;
}
.lede { font-size: 1.08rem; color: var(--ink-soft); margin-bottom: 2.2rem; }
h2 {
  font-size: 1.45rem; font-weight: 700; color: var(--ink);
  letter-spacing: -0.01em; margin: 2.8rem 0 1rem;
  padding-bottom: 0.5rem; border-bottom: 1px solid var(--line);
  scroll-margin-top: 1.5rem;
}
h3 {
  font-size: 1.1rem; font-weight: 700; color: var(--ink);
  margin: 1.9rem 0 0.7rem; scroll-margin-top: 1.5rem;
}
p { margin-bottom: 1rem; }
.content a { color: var(--accent); text-decoration: none; border-bottom: 1px solid rgba(217,119,87,0.3); }
.content a:hover { border-bottom-color: var(--accent); }
strong { color: var(--ink); font-weight: 700; }
ul, ol { margin: 0 0 1.1rem 1.3rem; }
li { margin-bottom: 0.45rem; }
li::marker { color: var(--accent); }

/* ---------- Code ---------- */
code {
  font-family: 'SF Mono', 'JetBrains Mono', Menlo, Consolas, monospace;
  font-size: 0.86em;
  background: var(--code-bg);
  color: #9A4B2E;
  padding: 0.1rem 0.38rem; border-radius: 5px;
}
pre {
  background: #2B2722;
  color: #EDE6DA;
  border-radius: var(--radius);
  padding: 1.15rem 1.3rem;
  overflow-x: auto;
  margin: 0 0 1.4rem;
  font-size: 0.85rem;
  line-height: 1.6;
  border: 1px solid #3A352E;
}
pre code { background: none; color: inherit; padding: 0; font-size: inherit; }
pre .c { color: #8B857B; }      /* comment */
pre .k { color: #E0936B; }      /* keyword */
pre .s { color: #9FB88A; }      /* string */
pre .f { color: #87A7C7; }      /* func/type */

/* ---------- Components ---------- */
.card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.3rem 1.5rem;
  margin-bottom: 1.4rem;
  box-shadow: 0 1px 3px rgba(60,50,40,0.04);
}
.card h3 { margin-top: 0; }

.callout {
  border-left: 3px solid var(--accent);
  background: var(--surface-alt);
  border-radius: 0 8px 8px 0;
  padding: 0.9rem 1.2rem;
  margin: 0 0 1.4rem;
  font-size: 0.95rem;
}
.callout.note { border-left-color: var(--blue); }
.callout.tip { border-left-color: var(--green); }
.callout .tag {
  font-weight: 700; font-size: 0.74rem; text-transform: uppercase;
  letter-spacing: 0.05em; color: var(--accent); margin-right: 0.4rem;
}
.callout.note .tag { color: var(--blue); }
.callout.tip .tag { color: var(--green); }

table {
  width: 100%; border-collapse: collapse; margin: 0 0 1.5rem;
  font-size: 0.88rem; background: var(--surface);
  border: 1px solid var(--line); border-radius: var(--radius); overflow: hidden;
}
th, td { text-align: left; padding: 0.65rem 0.9rem; border-bottom: 1px solid var(--line); }
th { background: var(--surface-alt); font-weight: 700; color: var(--ink); font-size: 0.8rem;
  text-transform: uppercase; letter-spacing: 0.03em; }
tr:last-child td { border-bottom: none; }
td code { font-size: 0.82em; }

/* grid of feature tiles */
.grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 1rem; margin-bottom: 1.5rem; }
.tile {
  background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 1.1rem 1.25rem; text-decoration: none !important; display: block;
  transition: transform 0.12s, box-shadow 0.12s, border-color 0.12s;
}
.tile:hover { transform: translateY(-2px); box-shadow: 0 6px 18px rgba(60,50,40,0.08); border-color: var(--accent); }
.tile .t-icon {
  margin-bottom: 0.65rem;
  width: 38px; height: 38px; border-radius: 9px;
  display: grid; place-items: center;
  background: var(--accent-soft);
}
.tile .t-icon svg { width: 20px; height: 20px; stroke: var(--accent); stroke-width: 2; }
.tile .t-title { font-weight: 700; color: var(--ink); margin-bottom: 0.25rem; border: none !important; }
.tile .t-desc { font-size: 0.83rem; color: var(--muted); }

/* sequence / flow diagram (SVG) */
.diagram {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1rem 1.2rem;
  margin: 0 0 1.5rem;
  box-shadow: 0 1px 3px rgba(60,50,40,0.04);
}
.diagram svg { width: 100%; height: auto; display: block; }
.diagram .actor rect { fill: var(--accent-soft); stroke: var(--accent); stroke-width: 1.2; }
.diagram .actor text {
  fill: var(--accent); font-weight: 700; font-size: 14px; text-anchor: middle;
  font-family: inherit;
}
.diagram .lifeline { stroke: var(--line); stroke-width: 1.5; stroke-dasharray: 4 4; }
.diagram .msg { stroke: var(--accent); stroke-width: 2; }
.diagram .msg.dash { stroke: var(--blue); stroke-dasharray: 6 4; }
.diagram .selfbox { fill: var(--surface-alt); stroke: var(--green); stroke-width: 1.3; }
.diagram .selfbox.ok { stroke: var(--green); fill: #EAF2EC; }
.diagram .step {
  fill: var(--ink); font-size: 13px; font-weight: 600; text-anchor: middle;
  font-family: inherit;
}
.diagram .lbl {
  fill: var(--ink); font-size: 12.5px; font-weight: 600; text-anchor: middle;
  font-family: inherit;
}
.diagram .note {
  fill: var(--muted); font-size: 11.5px; text-anchor: middle;
  font-family: inherit;
}

/* step badges */
.steps { counter-reset: step; list-style: none; margin-left: 0; }
.steps > li { position: relative; padding-left: 2.6rem; margin-bottom: 1rem; }
.steps > li::before {
  counter-increment: step; content: counter(step);
  position: absolute; left: 0; top: 0;
  width: 1.7rem; height: 1.7rem; border-radius: 50%;
  background: var(--accent); color: #fff; font-weight: 700; font-size: 0.85rem;
  display: grid; place-items: center;
}

/* page footer nav */
.page-nav { display: flex; justify-content: space-between; gap: 1rem; margin-top: 3.5rem;
  padding-top: 1.5rem; border-top: 1px solid var(--line); }
.page-nav a {
  flex: 1; border: 1px solid var(--line) !important; border-radius: var(--radius);
  padding: 0.85rem 1.1rem; text-decoration: none; background: var(--surface);
  transition: border-color 0.12s, box-shadow 0.12s;
}
.page-nav a:hover { border-color: var(--accent) !important; box-shadow: 0 4px 12px rgba(60,50,40,0.06); }
.page-nav .dir { font-size: 0.72rem; color: var(--muted); text-transform: uppercase; letter-spacing: 0.05em; }
.page-nav .ttl { font-weight: 700; color: var(--ink); }
.page-nav .next { text-align: right; }

.foot { color: var(--muted); font-size: 0.75rem; text-align: center; margin-top: 3rem; }

.pill { display:inline-block; font-size:0.72rem; font-weight:600; padding:0.12rem 0.55rem;
  border-radius: 20px; background: var(--accent-soft); color: var(--accent); margin-left: 0.4rem; }
.pill.green { background:#EAF2EC; color: var(--green);}
.pill.blue { background:#EAEFF6; color: var(--blue);}
.pill.gold { background:#F7F0DE; color: var(--gold);}

/* mobile */
.menu-btn { display:none; }
@media (max-width: 900px) {
  .layout { flex-direction: column; }
  .sidebar { position: static; width: 100%; height: auto; flex-basis: auto;
    border-right: none; border-bottom: 1px solid var(--line); }
  .content { padding: 2rem 1.25rem 4rem; }
  h1 { font-size: 1.7rem; }
}