:root {
  --bg: #e6eef0;
  --bg-accent: #f4efe6;
  --ink: #142226;
  --muted: #5d7176;
  --accent: #0f6b66;
  --accent-2: #c4842a;
  --card: rgba(255, 252, 247, .72);
  --line: rgba(20, 34, 38, .1);
  --shadow: 0 16px 40px rgba(20, 40, 44, .08);
  --danger: #9d3b32;
  --ok: #1d7a4d;
  --sidebar: rgba(15, 42, 46, .94);
  --sidebar-ink: #e7f2f1;
  color-scheme: light;
}
[data-theme="dark"] {
  --bg: #10181b;
  --bg-accent: #1a2428;
  --ink: #e7f1f2;
  --muted: #9eb0b4;
  --accent: #3dbeb6;
  --accent-2: #e0a45a;
  --card: rgba(22, 34, 38, .72);
  --line: rgba(231, 241, 242, .12);
  --shadow: 0 16px 40px rgba(0, 0, 0, .28);
  --sidebar: rgba(8, 14, 16, .92);
  color-scheme: dark;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  background:
    radial-gradient(1200px 500px at 10% -10%, rgba(15, 107, 102, .18), transparent 50%),
    radial-gradient(900px 400px at 100% 0%, rgba(196, 132, 42, .16), transparent 46%),
    var(--bg);
  font-family: "Source Sans 3", "Segoe UI", sans-serif;
}
h1, h2, h3, .brand-mark { font-family: Fraunces, Georgia, serif; font-weight: 560; letter-spacing: -.02em; }
a { color: var(--accent); text-decoration: none; }
.app-shell { display: grid; grid-template-columns: 250px 1fr; min-height: 100vh; }
.sidebar {
  position: sticky; top: 0; height: 100vh; overflow: auto;
  background: var(--sidebar); color: var(--sidebar-ink); padding: 1.2rem 1rem 2rem;
  display: flex; flex-direction: column; gap: .35rem;
}
.brand { display: flex; gap: .7rem; align-items: center; padding: .2rem .4rem 1rem; }
.brand-mark { font-size: 1.35rem; }
.brand small { display: block; color: #b7c9c8; font-family: "Source Sans 3", sans-serif; letter-spacing: .04em; }
.nav-label { margin: .85rem .45rem .15rem; font-size: .72rem; letter-spacing: .14em; text-transform: uppercase; color: #8fb0ad; }
.nav-link {
  color: var(--sidebar-ink); border-radius: 12px; padding: .48rem .75rem; display: flex; gap: .55rem; align-items: center;
}
.nav-link:hover, .nav-link.active { background: rgba(255,255,255,.1); color: white; }
.nav-link.active { box-shadow: inset 3px 0 0 #8fe3da; }
.nav-toggle { display: none; }
.page-head { display: flex; justify-content: space-between; gap: 1rem; align-items: flex-end; margin-bottom: 1rem; }
.page-head h1 { margin: 0; }
.stat-grid.primary { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.stat-grid.primary .value { font-size: 2.05rem; }
.stat-grid.secondary { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.stat.secondary .value { font-size: 1.2rem; }
.main { padding: 1.2rem 1.3rem 3rem; }
.topbar { display: flex; justify-content: space-between; gap: 1rem; align-items: center; margin-bottom: 1rem; }
.glass {
  background: var(--card); backdrop-filter: blur(16px); border: 1px solid var(--line);
  border-radius: 18px; box-shadow: var(--shadow);
}
.card-pad { padding: 1rem 1.05rem; }
.stat-grid, .card-grid { display: grid; gap: .8rem; }
.stat-grid { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.card-grid.two { grid-template-columns: 1.4fr .8fr; }
.card-grid.charts { grid-template-columns: 1fr 1fr; }
.stat .label { color: var(--muted); font-size: .82rem; }
.stat .value { font-size: 1.55rem; font-variant-numeric: tabular-nums; }
.muted { color: var(--muted); }
.btn-rain {
  background: var(--accent); color: white; border: 0; border-radius: 999px; padding: .55rem 1rem; font-weight: 650;
}
.btn-ghost { background: transparent; color: var(--ink); border: 1px solid var(--line); border-radius: 999px; padding: .45rem .8rem; }
.table-wrap { overflow: auto; }
table.data { width: 100%; border-collapse: collapse; font-size: .95rem; }
table.data th, table.data td { padding: .55rem .45rem; border-bottom: 1px solid var(--line); text-align: left; vertical-align: top; }
.tabs { display: flex; gap: .35rem; flex-wrap: wrap; margin-bottom: .8rem; }
.tabs a { border-radius: 999px; padding: .35rem .7rem; background: rgba(255,255,255,.35); color: var(--ink); }
.tabs a.active { background: var(--accent); color: white; }
.map { height: 420px; border-radius: 18px; }
.chart-box { min-height: 280px; }
.alert-item { padding: .7rem 0; border-bottom: 1px solid var(--line); }
.wizard-steps { display: flex; gap: .4rem; margin-bottom: 1rem; }
.wizard-steps span { flex: 1; text-align: center; padding: .4rem; border-radius: 999px; background: rgba(15,107,102,.08); font-size: .85rem; }
.wizard-steps span.on { background: var(--accent); color: white; }
.step { display: none; }
.step.on { display: block; }
.katex-display { overflow-x: auto; }
.formula-card { min-height: 180px; }
.badge { border-radius: 999px; padding: .15rem .5rem; background: rgba(15,107,102,.12); font-size: .78rem; }
.login-wrap { max-width: 460px; margin: 8vh auto; }
form .field { margin-bottom: .75rem; }
label { display: block; font-size: .86rem; margin-bottom: .2rem; }
input, select, textarea { width: 100%; border-radius: 12px; border: 1px solid var(--line); background: transparent; color: var(--ink); padding: .55rem .7rem; }
input[type="checkbox"] { width: auto; padding: 0; }
.warning { border-left: 4px solid var(--accent-2); padding: .6rem .8rem; }
.question-sheet { max-width: 760px; margin: 0 auto; padding: 0; overflow: hidden; }
.question-sheet > header, .question-sheet > section { padding: 1.15rem 1.35rem; border-bottom: 1px solid var(--line); }
.question-sheet > section:last-child { border-bottom: 0; }
.q-kicker { letter-spacing: .16em; font-size: .78rem; color: var(--muted); margin: 0 0 .35rem; }
.q-answer { font-size: clamp(2.4rem, 6vw, 3.4rem); text-align: center; margin: .2rem 0; font-variant-numeric: tabular-nums; }
.q-period { text-align: center; color: var(--muted); margin: 0; }
.worked-line { display: flex; justify-content: space-between; gap: 1rem; font-variant-numeric: tabular-nums; padding: .18rem 0; }
.worked-line.total { border-top: 1px solid var(--ink); margin-top: .45rem; padding-top: .5rem; font-weight: 700; }
.q-actions { display: flex; flex-wrap: wrap; gap: .55rem; }
.chain { list-style: none; margin: 0; padding: 0; display: flex; gap: .65rem; overflow-x: auto; }
.chain li {
  display: flex; flex-direction: column; gap: .25rem; min-width: 9.2rem; flex: 1;
  padding: .75rem .8rem; border-radius: 16px; background: rgba(15, 107, 102, .08);
}
.chain span { color: var(--muted); font-size: .78rem; letter-spacing: .04em; text-transform: uppercase; }
.chain-note { color: var(--muted); font-size: .92rem; text-transform: none; letter-spacing: 0; }
.box-row { display: grid; grid-template-columns: 9rem 1fr; gap: .6rem; align-items: center; margin-bottom: .45rem; }
.box-canvas { width: 100%; height: 56px; }
@media (max-width: 980px) {
  .app-shell { grid-template-columns: 1fr; }
  .nav-toggle { display: inline-flex; }
  .sidebar { display: none; position: relative; height: auto; }
  .sidebar.open { display: flex; }
  .stat-grid, .stat-grid.primary, .stat-grid.secondary, .card-grid.two, .card-grid.charts, .box-row { grid-template-columns: 1fr; }
  .page-head { flex-direction: column; align-items: flex-start; }
}