:root {
  color-scheme: dark;
  --panel: rgba(18, 19, 22, 0.82);
  --panel-border: rgba(255, 255, 255, 0.12);
  --text: #f7f7f7;
  --muted: rgba(255, 255, 255, 0.58);
  --button: rgba(255, 255, 255, 0.94);
  --button-text: #171717;
  --soft: rgba(255, 255, 255, 0.10);
  --soft-hover: rgba(255, 255, 255, 0.16);
}

* { box-sizing: border-box; }

html, body {
  width: 100%;
  height: 100%;
  margin: 0;
  overflow: hidden;
  background: #08090a;
  font-family: Inter, "Segoe UI", "Microsoft YaHei", sans-serif;
}

body { user-select: none; }

#app {
  position: fixed;
  inset: 0;
  overflow: hidden;
  background: #08090a;
}

#animation {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  display: block;
  cursor: default;
}

.top-button {
  position: absolute;
  top: max(18px, env(safe-area-inset-top));
  right: max(18px, env(safe-area-inset-right));
  z-index: 20;
}

.icon-button {
  width: 44px;
  height: 44px;
  border: 1px solid rgba(255,255,255,.15);
  border-radius: 50%;
  color: rgba(255,255,255,.86);
  background: rgba(0,0,0,.20);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  font-size: 22px;
  cursor: pointer;
  transition: opacity .25s ease, transform .25s ease, background .25s ease;
}

.icon-button:hover { background: rgba(0,0,0,.42); transform: scale(1.05); }

.empty-state {
  position: absolute;
  inset: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  gap: 12px;
  background: radial-gradient(circle at center, rgba(255,255,255,.04), rgba(0,0,0,.30));
  transition: opacity .45s ease, visibility .45s ease;
}

.empty-state.hidden { opacity: 0; visibility: hidden; pointer-events: none; }

.upload-button {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 14px 20px;
  border: 0;
  border-radius: 999px;
  background: var(--button);
  color: var(--button-text);
  font-size: 15px;
  font-weight: 650;
  cursor: pointer;
  box-shadow: 0 12px 40px rgba(0,0,0,.25);
  transition: transform .2s ease;
}

.upload-button:hover { transform: translateY(-2px); }
.upload-symbol { font-size: 20px; line-height: 1; }
.empty-state p { margin: 0; color: var(--muted); font-size: 12px; }

.controls {
  position: absolute;
  left: 50%;
  bottom: max(18px, env(safe-area-inset-bottom));
  z-index: 20;
  display: flex;
  align-items: center;
  gap: 18px;
  width: max-content;
  max-width: calc(100vw - 28px);
  padding: 13px 15px;
  border: 1px solid var(--panel-border);
  border-radius: 20px;
  background: var(--panel);
  backdrop-filter: blur(22px) saturate(1.15);
  -webkit-backdrop-filter: blur(22px) saturate(1.15);
  box-shadow: 0 18px 50px rgba(0,0,0,.28);
  transform: translate(-50%, 0);
  opacity: 0;
  visibility: hidden;
  transition: opacity .3s ease, visibility .3s ease, transform .3s ease;
}

#app.controls-visible .controls,
.controls:hover {
  opacity: 1;
  visibility: visible;
}

#app.controls-visible .controls { transform: translate(-50%, -2px); }

.control-group { display: flex; align-items: center; gap: 10px; }
.control-label { color: rgba(255,255,255,.65); font-size: 12px; white-space: nowrap; }
.control-label output { margin-left: 5px; color: #fff; font-variant-numeric: tabular-nums; }

.choice-row { display: flex; gap: 5px; padding: 3px; border-radius: 11px; background: rgba(255,255,255,.07); }
.choice-button, .soft-button, .main-button {
  border: 0;
  border-radius: 10px;
  font: inherit;
  cursor: pointer;
  white-space: nowrap;
  transition: background .18s ease, color .18s ease, transform .18s ease;
}

.choice-button {
  min-width: 36px;
  height: 30px;
  color: rgba(255,255,255,.65);
  background: transparent;
  font-size: 12px;
}
.choice-button:hover { color: #fff; background: rgba(255,255,255,.08); }
.choice-button.active { color: #171717; background: #fff; }

input[type="range"] {
  width: 130px;
  accent-color: #fff;
  cursor: pointer;
}

.main-button {
  padding: 10px 14px;
  color: var(--button-text);
  background: var(--button);
  font-size: 13px;
  font-weight: 650;
}
.main-button:hover { transform: translateY(-1px); }

.soft-button {
  padding: 9px 12px;
  color: rgba(255,255,255,.86);
  background: var(--soft);
  font-size: 12px;
}
.soft-button:hover { background: var(--soft-hover); }
.soft-button.active { color: #171717; background: #fff; }

.drop-hint {
  position: absolute;
  left: 50%;
  top: 50%;
  z-index: 30;
  padding: 12px 18px;
  border-radius: 999px;
  color: #171717;
  background: rgba(255,255,255,.94);
  font-size: 13px;
  pointer-events: none;
  opacity: 0;
  transform: translate(-50%, -50%) scale(.96);
  transition: opacity .2s ease, transform .2s ease;
}

#app.dragging .drop-hint { opacity: 1; transform: translate(-50%, -50%) scale(1); }

.toast {
  position: absolute;
  left: 50%;
  bottom: 110px;
  z-index: 40;
  padding: 9px 13px;
  border-radius: 999px;
  color: #171717;
  background: rgba(255,255,255,.92);
  font-size: 12px;
  opacity: 0;
  pointer-events: none;
  transform: translate(-50%, 8px);
  transition: opacity .25s ease, transform .25s ease;
}
.toast.show { opacity: 1; transform: translate(-50%, 0); }

@media (max-width: 760px) {
  .controls {
    gap: 9px;
    padding: 10px;
    border-radius: 17px;
    flex-wrap: wrap;
    justify-content: center;
  }
  .speed-group { order: 3; width: 100%; justify-content: center; }
  .upload-group { order: 1; }
  .density-group { order: 2; }
  .action-group { order: 4; }
}

@media (prefers-reduced-motion: reduce) {
  .controls, .toast, .drop-hint, .empty-state { transition-duration: .01ms; }
}

/* 照片锁定后，必须先清除才能重新选择 */
.main-button:disabled {
  opacity: .42;
  cursor: not-allowed;
  pointer-events: none;
}