:root {
  --bg1: #1a2035;
  --bg2: #0d1120;
  --panel: #1f2640;
  --panel-border: #39415e;
  --text: #e8ebf5;
  --text-dim: #9aa3bf;
  --accent: #4f7cff;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  height: 100%;
  overflow: hidden;
  font-family: "Segoe UI", system-ui, -apple-system, sans-serif;
  color: var(--text);
  background: radial-gradient(ellipse at 50% 30%, var(--bg1) 0%, var(--bg2) 75%);
}

#topbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  display: flex;
  align-items: center;
  gap: 18px;
  padding: 10px 18px;
  z-index: 10;
  user-select: none;
}

#topbar h1 {
  font-size: 22px;
  margin: 0;
  white-space: nowrap;
}

#toolbar { display: flex; gap: 10px; flex-wrap: wrap; }

button {
  background: #eef1f7;
  color: #1b2030;
  border: 1px solid #c9cfdd;
  border-radius: 8px;
  padding: 8px 18px;
  font-size: 15px;
  cursor: pointer;
  transition: transform 0.05s, background 0.15s;
}
button:hover { background: #ffffff; }
button:active { transform: scale(0.97); }
button:disabled { opacity: 0.45; cursor: default; }

#btnSettings { padding: 8px 12px; font-size: 16px; }

#stats {
  margin-left: auto;
  display: flex;
  gap: 22px;
  font-size: 15px;
  color: var(--text-dim);
  white-space: nowrap;
}
#stats b { color: var(--text); font-weight: 600; }

#scene {
  position: fixed;
  inset: 0;
  touch-action: none;
}
#scene canvas { display: block; }

#helpbar {
  position: fixed;
  left: 0; right: 0; bottom: 0;
  text-align: center;
  padding: 12px 8px;
  font-size: 14px;
  color: var(--text-dim);
  user-select: none;
  pointer-events: none;
}
#helpbar b { color: var(--text); }

/* ---- Panels ---- */
#editPanel, #settingsPanel {
  position: fixed;
  top: 70px;
  right: 18px;
  width: 230px;
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: 12px;
  padding: 14px 16px;
  z-index: 20;
  box-shadow: 0 8px 30px rgba(0,0,0,0.45);
}

.panel-title { font-weight: 600; margin-bottom: 10px; }
.panel-hint { font-size: 12.5px; color: var(--text-dim); line-height: 1.45; }

.panel-buttons { display: flex; gap: 8px; margin-top: 10px; }
.panel-buttons button { flex: 1; padding: 7px 0; font-size: 14px; }
button.primary { background: var(--accent); border-color: var(--accent); color: #fff; }
button.primary:hover { background: #6890ff; }

#palette {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
}
.swatch {
  height: 44px;
  border-radius: 8px;
  border: 2px solid rgba(255,255,255,0.18);
  cursor: pointer;
}
.swatch.selected {
  border-color: #fff;
  box-shadow: 0 0 0 2px var(--accent);
}

#settingsPanel label {
  display: block;
  font-size: 14px;
  color: var(--text-dim);
  margin-bottom: 12px;
}
#settingsPanel input[type=range] { width: 100%; margin-top: 6px; }
#settingsPanel label.row { display: flex; align-items: center; gap: 8px; }

/* ---- Tutor panel ---- */
button.accent { background: #ffce3a; border-color: #e3b51f; }
button.accent:hover { background: #ffd95e; }

#tutorPanel {
  position: fixed;
  top: 70px;
  left: 18px;
  bottom: 56px;
  width: 320px;
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: 12px;
  padding: 14px 16px;
  z-index: 20;
  box-shadow: 0 8px 30px rgba(0,0,0,0.45);
  display: flex;
  flex-direction: column;
  overflow-y: auto;
}

.tutor-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-weight: 600;
  font-size: 16px;
  margin-bottom: 10px;
}
.icon-btn {
  background: none;
  border: none;
  color: var(--text-dim);
  font-size: 22px;
  padding: 0 4px;
  line-height: 1;
}
.icon-btn:hover { color: var(--text); background: none; }

#tutorStages {
  list-style: none;
  margin: 0 0 12px;
  padding: 0;
  font-size: 13px;
  color: var(--text-dim);
}
#tutorStages li {
  padding: 3px 0 3px 24px;
  position: relative;
}
#tutorStages li::before {
  content: '○';
  position: absolute;
  left: 4px;
}
#tutorStages li.done { color: #7fd98a; }
#tutorStages li.done::before { content: '✔'; }
#tutorStages li.current {
  color: var(--text);
  font-weight: 600;
}
#tutorStages li.current::before { content: '▶'; color: #ffce3a; }

#tutorCard {
  background: rgba(255,255,255,0.04);
  border: 1px solid var(--panel-border);
  border-radius: 10px;
  padding: 12px 14px;
}
#tutorStageTag {
  font-size: 11.5px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: #ffce3a;
  margin-bottom: 4px;
}
#tutorCard h3 { margin: 0 0 8px; font-size: 16px; }
#tutorCard p { margin: 0 0 10px; font-size: 13.5px; line-height: 1.5; color: var(--text-dim); }
#tutorCard p b { color: var(--text); }

#tutorHands {
  background: rgba(255, 206, 58, 0.10);
  border-left: 3px solid #ffce3a;
  border-radius: 0 8px 8px 0;
  padding: 8px 10px;
  margin-bottom: 10px;
  font-size: 13px;
  line-height: 1.5;
  color: var(--text);
}
#tutorHands:empty { display: none; }

#tutorAlg { margin-bottom: 10px; }
#tutorAlg span {
  display: inline-block;
  background: #2b3352;
  border: 1px solid var(--panel-border);
  border-radius: 6px;
  padding: 3px 8px;
  margin: 0 4px 4px 0;
  font-family: Consolas, monospace;
  font-size: 14px;
  color: var(--text);
}
#tutorAlg span.done {
  opacity: 0.35;
  text-decoration: line-through;
}
#tutorAlg span.cur {
  background: #ffce3a;
  border-color: #ffce3a;
  color: #1b2030;
  font-weight: 700;
  box-shadow: 0 0 8px rgba(255, 206, 58, 0.6);
}

#tutorNotation { margin-top: 10px; font-size: 12.5px; color: var(--text-dim); }
#tutorNotation summary { cursor: pointer; color: var(--accent); }
#tutorNotation p { margin: 6px 0 0; line-height: 1.5; }

#tutorFoot { margin-top: auto; padding-top: 10px; }

@media (max-width: 900px) {
  #tutorPanel {
    left: 8px; right: 8px; width: auto;
    top: auto; bottom: 40px; max-height: 45vh;
  }
}

/* ---- Scan panel ---- */
#scanPanel {
  position: fixed;
  top: 70px;
  left: 50%;
  transform: translateX(-50%);
  width: min(420px, 94vw);
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: 12px;
  padding: 14px 16px;
  z-index: 25;
  box-shadow: 0 8px 30px rgba(0,0,0,0.5);
}
#scanPanel small { color: var(--text-dim); font-weight: 400; margin-left: 8px; }

#scanStage {
  position: relative;
  border-radius: 10px;
  overflow: hidden;
  background: #000;
}
#scanVideo { width: 100%; display: block; }

#scanGrid {
  position: absolute;
  top: 50%; left: 50%;
  width: 62%;
  aspect-ratio: 1;
  transform: translate(-50%, -50%);
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  pointer-events: none;
}
#scanGrid i {
  border: 2px solid rgba(255, 206, 58, 0.9);
  box-shadow: inset 0 0 0 1px rgba(0,0,0,0.5);
}

#scanInstr {
  font-size: 13.5px;
  line-height: 1.5;
  color: var(--text-dim);
  margin: 10px 0;
}
#scanInstr b { color: var(--text); }

#scanThumbs { display: flex; gap: 6px; margin-bottom: 10px; }
.scan-mini {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  width: 42px; height: 42px;
  gap: 1px;
  background: var(--panel-border);
  border: 2px solid transparent;
  border-radius: 4px;
}
.scan-mini.active { border-color: #ffce3a; }
.scan-mini i { background: #11152a; }

/* ---- Toast ---- */
#toast {
  position: fixed;
  bottom: 56px;
  left: 50%;
  transform: translateX(-50%);
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: 10px;
  padding: 10px 22px;
  font-size: 15px;
  z-index: 30;
  box-shadow: 0 6px 24px rgba(0,0,0,0.4);
  transition: opacity 0.25s;
  pointer-events: none;
  max-width: 90vw;
  text-align: center;
}

.hidden { display: none !important; }

@media (max-width: 760px) {
  #topbar { flex-wrap: wrap; gap: 8px; padding: 8px 10px; }
  #topbar h1 { font-size: 18px; width: 100%; }
  button { padding: 6px 12px; font-size: 13px; }
  #stats { gap: 12px; font-size: 13px; margin-left: 0; }
  #helpbar { font-size: 11px; }
}