/* CSIT745 v2 — shared Explorer / Practice styles */
:root {
  --ink: #15231c;
  --muted: #4a5c52;
  --paper: #f3f6f1;
  --panel: rgba(255, 255, 255, 0.82);
  --line: rgba(21, 35, 28, 0.12);
  --accent: #0f6b4c;
  --accent-2: #c45c26;
  --accent-soft: #d8efe4;
  --warn: #8a3b12;
  --ok: #1f7a4d;
  --bad: #a33b3b;
  --shadow: 0 18px 50px rgba(21, 35, 28, 0.12);
  --radius: 18px;
  --font-display: "Fraunces", Georgia, serif;
  --font-body: "Source Sans 3", "Segoe UI", sans-serif;
  --tree-w: 300px;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  color: var(--ink);
  font-family: var(--font-body);
  background:
    radial-gradient(1200px 600px at 10% -10%, #d7ebe0 0%, transparent 55%),
    radial-gradient(900px 500px at 100% 0%, #f3dfd0 0%, transparent 45%),
    linear-gradient(180deg, #eef4ef 0%, var(--paper) 40%, #e7eee8 100%);
  min-height: 100vh;
}
a { color: var(--accent); }
.wrap { width: min(1200px, calc(100% - 2rem)); margin: 0 auto; padding: 1.25rem 0 3rem; }
.site-nav {
  display: flex; flex-wrap: wrap; gap: 0.45rem; align-items: center;
  margin: 0 0 0.75rem; padding: 0.55rem 0.65rem; border-radius: 999px;
  border: 1px solid var(--line); background: rgba(255,255,255,0.82);
  backdrop-filter: blur(8px); width: fit-content; max-width: 100%;
}
.site-nav a {
  border: 1px solid transparent; background: transparent; color: var(--ink);
  border-radius: 999px; padding: 0.4rem 0.85rem; font: inherit; font-weight: 700;
  font-size: 0.92rem; text-decoration: none;
}
.site-nav a:hover { background: var(--accent-soft); color: var(--accent); }
.site-nav a.home { background: var(--accent); color: #fff; }
.site-nav a.here { background: var(--accent-soft); color: var(--accent); }
.kicker {
  color: var(--accent); font-weight: 700; letter-spacing: 0.04em;
  text-transform: uppercase; font-size: 0.78rem; margin: 0 0 0.35rem;
}
h1 {
  font-family: var(--font-display); font-weight: 650;
  font-size: clamp(1.7rem, 3.5vw, 2.4rem); line-height: 1.15;
  margin: 0.15rem 0 0.4rem; letter-spacing: -0.02em;
}
.lede { margin: 0; max-width: 42rem; color: var(--muted); font-size: 1.02rem; }
.panel {
  background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius);
  box-shadow: var(--shadow); backdrop-filter: blur(10px); padding: 1rem 1.1rem;
}
.btn, button.btn {
  appearance: none; border: 1px solid var(--line); background: var(--panel);
  color: var(--ink); border-radius: 999px; padding: 0.55rem 1rem;
  font: inherit; font-weight: 600; cursor: pointer; text-decoration: none;
  transition: transform 0.15s ease, border-color 0.15s ease;
}
.btn:hover, button.btn:hover { transform: translateY(-1px); border-color: rgba(15,107,76,0.35); }
.btn.primary { background: var(--accent); color: #fff; border-color: transparent; }
.btn.ghost { background: transparent; }
.btn:disabled { opacity: 0.45; cursor: not-allowed; transform: none; }
.chip {
  border: 1px solid var(--line); background: rgba(255,255,255,0.7);
  border-radius: 999px; padding: 0.35rem 0.8rem; font-weight: 600;
  cursor: pointer; font: inherit; font-size: 0.9rem;
}
.chip.active { background: var(--accent); color: #fff; border-color: transparent; }
.depth-row { display: flex; flex-wrap: wrap; gap: 0.4rem; margin: 0.75rem 0 0.5rem; }

/* Explorer layout */
.explorer {
  display: grid; grid-template-columns: var(--tree-w) 1fr; gap: 1rem; margin-top: 1rem;
  min-height: 70vh;
}
.tree-pane {
  overflow: auto; max-height: calc(100vh - 8rem); padding: 0.85rem;
  position: sticky; top: 0.75rem; align-self: start;
}
.tree-pane h2 {
  font-family: var(--font-display); font-size: 1.1rem; margin: 0 0 0.6rem;
}
.tree details { margin: 0.15rem 0; }
.tree summary {
  cursor: pointer; list-style: none; padding: 0.35rem 0.45rem; border-radius: 10px;
  font-weight: 650; font-size: 0.92rem;
}
.tree summary::-webkit-details-marker { display: none; }
.tree summary:hover { background: var(--accent-soft); }
.tree .leaf {
  display: block; width: 100%; text-align: left; border: none; background: transparent;
  padding: 0.32rem 0.55rem 0.32rem 0.9rem; border-radius: 10px; cursor: pointer;
  font: inherit; font-size: 0.88rem; color: var(--ink);
}
.tree .leaf:hover { background: rgba(15,107,76,0.08); }
.tree .leaf.active { background: var(--accent); color: #fff; font-weight: 650; }
.tree .mod-label { color: var(--muted); font-size: 0.78rem; font-weight: 700; margin: 0.55rem 0 0.2rem; text-transform: uppercase; letter-spacing: 0.04em; }
.panel-pane { padding: 1.15rem 1.25rem; min-height: 28rem; }
.panel-pane .title {
  font-family: var(--font-display); font-size: clamp(1.35rem, 2.5vw, 1.85rem);
  margin: 0 0 0.35rem; line-height: 1.2;
}
.source-line {
  color: var(--muted); font-size: 0.88rem; margin: 0.35rem 0 0.85rem;
}
.source-line code { font-size: 0.85em; background: rgba(21,35,28,0.06); padding: 0.1rem 0.35rem; border-radius: 6px; }
.quick-def {
  font-size: 1.08rem; line-height: 1.45; margin: 0 0 0.9rem;
  padding: 0.85rem 1rem; border-left: 3px solid var(--accent);
  background: rgba(216,239,228,0.45); border-radius: 0 12px 12px 0;
}
.key-ideas { margin: 0.5rem 0 0.9rem; padding-left: 1.15rem; }
.key-ideas li { margin: 0.35rem 0; }
.detail-block { color: var(--ink); line-height: 1.55; margin: 0.75rem 0; }
.detail-block p { margin: 0.55rem 0; }
.quote {
  margin: 0.85rem 0; padding: 0.75rem 1rem; border-radius: 12px;
  background: rgba(255,255,255,0.65); border: 1px dashed var(--line);
  font-style: italic; color: var(--muted); font-size: 0.95rem;
}
.compare-box, .example-box {
  margin: 0.75rem 0; padding: 0.75rem 0.95rem; border-radius: 12px;
  border: 1px solid var(--line); background: rgba(255,255,255,0.55);
}
.compare-box h3, .example-box h3, .related h3 {
  margin: 0 0 0.4rem; font-size: 0.95rem; color: var(--accent);
}
.related { margin-top: 1rem; }
.related a {
  display: inline-block; margin: 0.25rem 0.35rem 0.25rem 0;
  padding: 0.3rem 0.7rem; border-radius: 999px; border: 1px solid var(--line);
  text-decoration: none; color: var(--ink); font-weight: 600; font-size: 0.88rem;
  background: rgba(255,255,255,0.7);
}
.nav-concepts {
  display: flex; justify-content: space-between; gap: 0.5rem; flex-wrap: wrap;
  margin-top: 1.25rem; padding-top: 0.85rem; border-top: 1px solid var(--line);
}
.empty-hint { color: var(--muted); padding: 2rem 0.5rem; }

/* Practice */
.practice-head { display: flex; flex-wrap: wrap; gap: 0.75rem; align-items: flex-end; justify-content: space-between; }
.meta-row { display: flex; flex-wrap: wrap; gap: 0.75rem 1.2rem; color: var(--muted); font-size: 0.95rem; margin: 0.6rem 0 0; }
.meta-row strong { color: var(--ink); }
.q-card { margin-top: 1rem; }
.q-stem { font-size: 1.15rem; font-weight: 650; line-height: 1.4; margin: 0 0 1rem; }
.options { display: grid; gap: 0.55rem; }
.opt {
  display: block; width: 100%; text-align: left; padding: 0.75rem 0.95rem;
  border-radius: 14px; border: 1px solid var(--line); background: rgba(255,255,255,0.75);
  font: inherit; cursor: pointer; transition: border-color 0.15s, background 0.15s;
}
.opt:hover:not(:disabled) { border-color: rgba(15,107,76,0.4); }
.opt.correct { background: #e5f6ec; border-color: var(--ok); }
.opt.wrong { background: #f8e8e8; border-color: var(--bad); }
.opt:disabled { cursor: default; }
.feedback { margin-top: 0.85rem; padding: 0.75rem 0.95rem; border-radius: 12px; background: rgba(216,239,228,0.4); }
.feedback.bad { background: rgba(248,232,232,0.7); }
.session-end h2 { font-family: var(--font-display); margin: 0 0 0.5rem; }
.flag-list { margin: 0.75rem 0; padding-left: 1.1rem; }
.flag-list a { font-weight: 600; }
.progress-bar {
  height: 8px; border-radius: 999px; background: rgba(21,35,28,0.08); overflow: hidden; margin: 0.75rem 0 0;
}
.progress-bar > i { display: block; height: 100%; width: 0; background: linear-gradient(90deg, var(--accent), #2f9e74); border-radius: inherit; transition: width 0.25s ease; }

@media (max-width: 860px) {
  .explorer { grid-template-columns: 1fr; }
  .tree-pane { position: static; max-height: 16rem; }
}