:root {
  --bg: #08080a;
  --panel: rgba(18, 18, 22, 0.82);
  --line: rgba(255, 255, 255, 0.08);
  --text: #e8e8ec;
  --muted: #8a8a92;
  --accent: #7fd8c4;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  height: 100%;
  overflow: hidden;
  background: var(--bg);
  color: var(--text);
  font: 13px/1.4 ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}

#gpu {
  position: fixed;
  inset: 0;
  width: 100%;
  height: 100%;
  display: block;
  touch-action: none;
}

/* ---- control panel ---- */
#ui {
  position: fixed;
  top: 14px;
  left: 14px;
  width: 248px;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 12px;
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.45);
  user-select: none;
  z-index: 10;
}

#ui header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 11px 14px;
  font-weight: 600;
  letter-spacing: 0.2px;
  border-bottom: 1px solid var(--line);
}

#ui header button {
  width: 22px;
  height: 22px;
  border: none;
  border-radius: 6px;
  background: rgba(255, 255, 255, 0.06);
  color: var(--text);
  cursor: pointer;
  line-height: 1;
}

#ui .body {
  padding: 10px 14px 4px;
  display: flex;
  flex-direction: column;
  gap: 11px;
}

#ui.collapsed .body,
#ui.collapsed footer { display: none; }

#ui.hidden, #hint.hidden { display: none; }

.row {
  display: flex;
  align-items: center;
  gap: 10px;
}
.row > span:first-child {
  flex: 0 0 84px;
  color: var(--muted);
  white-space: nowrap;
}
.row.check { gap: 8px; }
.row.check span { color: var(--text); }
.row.colors { gap: 8px; justify-content: space-between; }
.row.colors label {
  display: flex;
  align-items: center;
  gap: 6px;
}
.row.colors span { color: var(--muted); }
.val {
  flex: 0 0 auto;
  width: 26px;
  text-align: right;
  color: var(--accent);
  font-variant-numeric: tabular-nums;
}

.sep {
  height: 1px;
  background: var(--line);
  margin: 1px 0;
}

.row.btns { gap: 8px; }
.row.btns button {
  flex: 1 1 0;
  min-width: 0;
  background: rgba(255, 255, 255, 0.06);
  color: var(--text);
  border: 1px solid var(--line);
  border-radius: 7px;
  padding: 6px;
  cursor: pointer;
}
.row.btns button:hover { background: rgba(255, 255, 255, 0.11); }

select, input[type="range"], button.full {
  flex: 1 1 auto;
  min-width: 0;
}

select {
  appearance: none;
  background: rgba(255, 255, 255, 0.06);
  color: var(--text);
  border: 1px solid var(--line);
  border-radius: 7px;
  padding: 5px 8px;
}

button.full {
  background: rgba(127, 216, 196, 0.14);
  color: var(--accent);
  border: 1px solid rgba(127, 216, 196, 0.3);
  border-radius: 7px;
  padding: 7px;
  cursor: pointer;
  font-weight: 600;
}
button.full:hover { background: rgba(127, 216, 196, 0.22); }

input[type="checkbox"] { accent-color: var(--accent); width: 15px; height: 15px; }
input[type="color"] {
  width: 30px;
  height: 22px;
  padding: 0;
  border: 1px solid var(--line);
  border-radius: 5px;
  background: none;
  cursor: pointer;
}

input[type="range"] {
  appearance: none;
  height: 4px;
  border-radius: 2px;
  background: rgba(255, 255, 255, 0.14);
  outline: none;
}
input[type="range"]::-webkit-slider-thumb {
  appearance: none;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--accent);
  cursor: pointer;
}
input[type="range"]::-moz-range-thumb {
  width: 14px;
  height: 14px;
  border: none;
  border-radius: 50%;
  background: var(--accent);
  cursor: pointer;
}

#ui footer {
  padding: 8px 14px 10px;
  color: var(--muted);
  border-top: 1px solid var(--line);
  font-variant-numeric: tabular-nums;
}

#hint {
  position: fixed;
  bottom: 12px;
  left: 50%;
  transform: translateX(-50%);
  color: var(--muted);
  font-size: 11.5px;
  letter-spacing: 0.3px;
  background: rgba(0, 0, 0, 0.3);
  padding: 6px 12px;
  border-radius: 20px;
  z-index: 10;
  white-space: nowrap;
}

#error {
  position: fixed;
  inset: 0;
  display: grid;
  place-items: center;
  background: var(--bg);
  z-index: 20;
  text-align: center;
  padding: 24px;
}
#error.hidden { display: none; }
#error h1 { color: #ff6b6b; font-size: 20px; margin: 0 0 8px; }
#error p { color: var(--text); margin: 0 0 12px; max-width: 480px; }
#error small { color: var(--muted); }

@media (max-width: 520px) {
  #hint { font-size: 10px; padding: 5px 9px; }
  #ui { width: calc(100vw - 28px); }
}