:root {
  --bg: #0d1117;
  --panel: #151b24;
  --panel-2: #1c2430;
  --line: #2a3442;
  --text: #e6edf3;
  --muted: #8b98a8;
  --accent: #58a6ff;
  --L: #ff9f1c;
  --tau: #ff4d6d;
  --w: #3ddbd9;
  --g: #7bd88f;
  --trail: #c792ea;
  color-scheme: dark;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 14px/1.55 -apple-system, BlinkMacSystemFont, "Apple SD Gothic Neo", "Pretendard", "Noto Sans KR", sans-serif;
}

button, select, input { font: inherit; color: inherit; }

.top {
  display: flex;
  flex-wrap: wrap;
  gap: 12px 24px;
  align-items: end;
  justify-content: space-between;
  padding: 16px 20px 10px;
}
.top h1 { margin: 0; font-size: 22px; letter-spacing: -0.02em; }
.top p { margin: 4px 0 0; color: var(--muted); }
.top p b { color: var(--L); font-weight: 600; }

.presets { display: flex; flex-wrap: wrap; gap: 6px; }
.presets button, .chips button, .transport button, .learn button[data-preset] {
  background: var(--panel-2);
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 5px 12px;
  cursor: pointer;
  transition: border-color .15s, background .15s;
}
.presets button:hover, .chips button:hover, .transport button:hover, .learn button:hover { border-color: var(--accent); }
.presets button.active { background: #1f3552; border-color: var(--accent); }

.layout {
  display: grid;
  grid-template-columns: 290px minmax(0, 1fr) 340px;
  gap: 12px;
  padding: 0 12px 12px;
  height: calc(100vh - 86px);
  min-height: 620px;
}

.panel {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 12px;
}

.controls { padding: 12px; overflow-y: auto; }
.controls section { border-top: 1px solid var(--line); margin-top: 12px; padding-top: 8px; }
.controls h2 { font-size: 13px; margin: 0 0 6px; }
.controls h2 small { color: var(--muted); font-weight: 400; margin-left: 4px; }

.transport { display: grid; grid-template-columns: 1fr 1fr; gap: 6px; margin-bottom: 6px; }
.transport button { border-radius: 8px; padding: 7px 8px; }
.transport button:disabled { opacity: .4; cursor: not-allowed; }
.transport .primary { background: #1f3552; border-color: var(--accent); }

.field { margin: 8px 0; }
.field .head { display: flex; justify-content: space-between; gap: 8px; }
.field label { color: var(--text); }
.field label small { color: var(--muted); }
.field output { font-variant-numeric: tabular-nums; color: var(--accent); white-space: nowrap; }
.field input[type=range] { width: 100%; accent-color: var(--accent); margin: 2px 0 0; }

.row { display: flex; justify-content: space-between; align-items: center; gap: 8px; margin: 8px 0; }
select { background: var(--panel-2); border: 1px solid var(--line); border-radius: 6px; padding: 3px 6px; }

.chips { display: flex; flex-wrap: wrap; gap: 4px; margin: -2px 0 8px; }
.chips button { padding: 2px 9px; font-size: 12px; }

.link { background: none; border: 0; padding: 0; color: var(--accent); cursor: pointer; font-size: 12px; text-align: left; }
.link:hover { text-decoration: underline; }

.check { display: flex; align-items: center; gap: 6px; margin: 5px 0; cursor: pointer; }
.sw { display: inline-block; width: 14px; height: 4px; border-radius: 2px; vertical-align: middle; }
.sw.L { background: var(--L); }
.sw.tau { background: var(--tau); }
.sw.w { background: var(--w); }
.sw.g { background: var(--g); }
.sw.trail { background: var(--trail); }

.stage { display: grid; grid-template-rows: minmax(0, 1fr) auto; gap: 12px; min-width: 0; }
.viewport { position: relative; border-radius: 12px; overflow: hidden; border: 1px solid var(--line); background: #0a0e14; min-height: 360px; }
.viewport canvas { display: block; width: 100%; height: 100%; }

.hud {
  position: absolute; top: 10px; left: 10px;
  display: grid; grid-template-columns: auto auto; gap: 1px 12px;
  background: rgba(13, 17, 23, .78); border: 1px solid var(--line); border-radius: 10px;
  padding: 8px 12px; font-size: 12.5px; font-variant-numeric: tabular-nums; pointer-events: none;
  backdrop-filter: blur(4px);
}
.hud dt { color: var(--muted); }
.hud dd { margin: 0; text-align: right; }
.hud .warn { color: var(--tau); }
.hud .note-row { color: var(--L); }
.hud .slow { color: var(--L); font-size: 11px; }

.legend {
  position: absolute; top: 10px; right: 10px;
  display: flex; flex-direction: column; gap: 2px;
  background: rgba(13, 17, 23, .7); border-radius: 8px; padding: 6px 10px; font-size: 12px; pointer-events: none;
}
.legend i { margin-right: 6px; }
.hint { position: absolute; bottom: 6px; right: 10px; margin: 0; color: var(--muted); font-size: 11px; pointer-events: none; }

.charts { padding: 8px 10px; }
.charts canvas { width: 100%; height: 220px; display: block; }

.learn { padding: 14px 16px; overflow-y: auto; }
.learn h2 { margin: 0 0 8px; font-size: 16px; }
.learn details { border-top: 1px solid var(--line); padding: 8px 0; }
.learn summary { cursor: pointer; font-weight: 600; font-size: 14.5px; }
.learn p, .learn li { color: #cdd6df; }
.learn ol, .learn ul { padding-left: 20px; margin: 6px 0; }
.learn li { margin: 3px 0; }
.learn button[data-preset] { padding: 1px 8px; font-size: 12.5px; }
.cL { color: var(--L); }
.cT { color: var(--tau); }
.eq { font-family: "STIX Two Math", "Cambria Math", "Times New Roman", serif; font-style: italic; background: var(--panel-2); padding: 1px 6px; border-radius: 4px; white-space: nowrap; }
.eq.big { display: block; text-align: center; font-size: 22px; padding: 10px; white-space: normal; }
.frac { display: inline-flex; flex-direction: column; vertical-align: middle; text-align: center; font-size: .8em; }
.frac span:first-child { border-bottom: 1px solid currentColor; padding: 0 4px; }
.live { background: #0f1a28; border: 1px solid #23405f; border-radius: 8px; padding: 8px 10px; font-size: 12.5px; font-variant-numeric: tabular-nums; }
.live b { color: var(--accent); }
.note { font-size: 12px; color: var(--muted) !important; }
.try { background: #1b2230; border-left: 3px solid var(--L); padding: 6px 10px; border-radius: 0 6px 6px 0; }
.shapes { display: grid; grid-template-columns: repeat(3, 1fr); gap: 6px; margin: 8px 0; }
.shapes button { display: flex; flex-direction: column; border-radius: 8px !important; padding: 6px !important; }
.shapes button span { font-size: 11px; color: var(--muted); }
.symbols { border-collapse: collapse; width: 100%; font-size: 12.5px; }
.symbols td { border-top: 1px solid var(--line); padding: 4px 6px; vertical-align: top; }
.symbols td:first-child { font-family: "STIX Two Math", "Times New Roman", serif; font-style: italic; white-space: nowrap; }
.source { font-size: 12px; color: var(--muted); border-top: 1px solid var(--line); padding-top: 8px; }
.source a { color: var(--accent); }

@media (max-width: 1180px) {
  .layout { grid-template-columns: 270px minmax(0, 1fr); height: auto; }
  .stage { min-height: 640px; }
  .learn { grid-column: 1 / -1; }
}
@media (max-width: 760px) {
  .layout { grid-template-columns: 1fr; }
  .stage { order: -1; grid-template-rows: 420px auto; min-height: 0; }
  .hud { font-size: 10.5px; padding: 5px 8px; gap: 0 8px; opacity: .9; }
  .hud > :nth-child(n + 9) { display: none; }
  .legend { display: none; }
}