:root {
  --bg1: #eef1ff;
  --bg2: #fdeaf3;
  --bg3: #e7f6f5;
  --ink: #2b2740;
  --ink-soft: #6b6786;
  --accent: #7c6ff0;
  --accent2: #f0a6c0;
  --card: rgba(255, 255, 255, 0.72);
  --line: rgba(124, 111, 240, 0.18);
  --shadow: 0 24px 60px -20px rgba(80, 70, 140, 0.35);
}

* { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: -apple-system, "PingFang SC", "Microsoft YaHei", "Segoe UI", sans-serif;
  color: var(--ink);
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 32px 16px;
  background: linear-gradient(135deg, var(--bg1), var(--bg2) 55%, var(--bg3));
  position: relative;
  overflow-x: hidden;
}

.aurora {
  position: fixed;
  inset: -20% -20% auto -20%;
  height: 70vh;
  background:
    radial-gradient(40% 50% at 20% 30%, rgba(124, 111, 240, 0.25), transparent 70%),
    radial-gradient(45% 45% at 80% 20%, rgba(240, 166, 192, 0.28), transparent 70%),
    radial-gradient(40% 40% at 55% 60%, rgba(150, 220, 220, 0.22), transparent 70%);
  filter: blur(20px);
  z-index: 0;
  pointer-events: none;
  animation: drift 18s ease-in-out infinite alternate;
}
@keyframes drift {
  from { transform: translate3d(0,0,0) scale(1); }
  to   { transform: translate3d(0,-18px,0) scale(1.06); }
}

.card {
  position: relative;
  z-index: 1;
  width: min(680px, 100%);
  background: var(--card);
  backdrop-filter: blur(18px);
  -webkit-backdrop-filter: blur(18px);
  border: 1px solid rgba(255, 255, 255, 0.6);
  border-radius: 24px;
  box-shadow: var(--shadow);
  padding: 40px 38px 28px;
}

.head { text-align: center; margin-bottom: 26px; }
.logo {
  display: inline-block;
  font-size: 13px;
  letter-spacing: 4px;
  color: var(--accent);
  border: 1px solid var(--line);
  padding: 4px 12px;
  border-radius: 999px;
  margin-bottom: 14px;
}
.head h1 {
  font-size: 27px;
  font-weight: 600;
  letter-spacing: 1px;
}
.sub {
  margin-top: 10px;
  color: var(--ink-soft);
  font-size: 13.5px;
  line-height: 1.7;
}

.drop {
  border: 1.5px dashed var(--line);
  border-radius: 18px;
  padding: 30px 20px;
  text-align: center;
  cursor: pointer;
  transition: border-color .2s, background .2s, transform .2s;
  background: rgba(255, 255, 255, 0.35);
}
.drop:hover, .drop.drag {
  border-color: var(--accent);
  background: rgba(124, 111, 240, 0.06);
  transform: translateY(-1px);
}
.drop-inner { pointer-events: none; }
.icon { width: 40px; height: 40px; color: var(--accent); }
.drop-title { margin-top: 12px; font-size: 15px; }
.link { color: var(--accent); font-weight: 600; }
.drop-hint { margin-top: 6px; color: var(--ink-soft); font-size: 12.5px; }

.file-info {
  display: flex;
  align-items: center;
  gap: 10px;
  justify-content: center;
  margin-top: 4px;
  font-size: 14px;
}
.file-info .dot {
  width: 8px; height: 8px; border-radius: 50%;
  background: #4cc9a0; box-shadow: 0 0 0 4px rgba(76,201,160,.18);
}
.clear {
  border: none; background: transparent; color: var(--ink-soft);
  font-size: 20px; line-height: 1; cursor: pointer; padding: 0 4px;
}
.clear:hover { color: var(--accent2); }

.opts { margin: 22px 0 18px; display: flex; gap: 14px; flex-wrap: wrap; }
.opt { display: flex; flex-direction: column; gap: 7px; flex: 1; min-width: 220px; }
.opt span { font-size: 13px; color: var(--ink-soft); }
.opt select {
  font: inherit; font-size: 14px;
  padding: 11px 13px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: rgba(255,255,255,.75);
  color: var(--ink);
  cursor: pointer;
}
.opt select:focus { outline: 2px solid var(--accent); outline-offset: 1px; }

.btn {
  width: 100%;
  padding: 14px;
  border: none;
  border-radius: 14px;
  background: linear-gradient(120deg, var(--accent), #9b8cf5);
  color: #fff;
  font-size: 15.5px;
  font-weight: 600;
  letter-spacing: 1px;
  cursor: pointer;
  transition: transform .15s, box-shadow .2s, opacity .2s;
  box-shadow: 0 12px 26px -10px rgba(124,111,240,.7);
}
.btn:hover:not(:disabled) { transform: translateY(-1px); }
.btn:disabled { opacity: .45; cursor: not-allowed; box-shadow: none; }

.progress { margin-top: 24px; text-align: center; }
.spinner {
  width: 30px; height: 30px; margin: 0 auto 12px;
  border: 3px solid var(--line);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin .8s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }
#progressText { color: var(--ink-soft); font-size: 13.5px; }

.error {
  margin-top: 20px;
  padding: 14px 16px;
  border-radius: 12px;
  background: rgba(240,120,140,.12);
  border: 1px solid rgba(240,120,140,.3);
  color: #c0395a;
  font-size: 13px;
  white-space: pre-wrap;
  word-break: break-word;
}

.results { margin-top: 26px; }
.results-title { font-size: 16px; font-weight: 600; margin-bottom: 14px; }
.stem-grid { display: grid; gap: 14px; }
.stem {
  display: flex; align-items: center; gap: 14px;
  padding: 14px 16px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: rgba(255,255,255,.6);
}
.stem .badge {
  flex: 0 0 auto;
  font-size: 12.5px; font-weight: 600;
  color: var(--accent);
  background: rgba(124,111,240,.1);
  padding: 6px 11px; border-radius: 9px;
}
.stem audio { flex: 1; min-width: 0; height: 36px; }
.stem .dl {
  flex: 0 0 auto;
  text-decoration: none;
  font-size: 13px; font-weight: 600;
  color: #fff;
  background: linear-gradient(120deg, var(--accent), #9b8cf5);
  padding: 9px 14px; border-radius: 10px;
  transition: transform .15s;
}
.stem .dl:hover { transform: translateY(-1px); }

.foot {
  margin-top: 26px; text-align: center;
  font-size: 11.5px; color: var(--ink-soft); opacity: .8;
}

.hidden { display: none !important; }