:root {
    color-scheme: light;
    --bg: #0b1020;
    --card: rgba(18, 25, 45, 0.78);
    --text: #e5e7eb;
    --muted: #9ca3af;
    --border: rgba(148, 163, 184, 0.18);
    --accent: #60a5fa;
    --accent-strong: #38bdf8;
    --danger: #f87171;
    --glow: 0 0 0 1px rgba(96, 165, 250, 0.2), 0 12px 30px rgba(15, 23, 42, 0.6);
  }
  
  * {
    box-sizing: border-box;
  }
  
  body {
    margin: 0;
    font-family: "Inter", "PingFang SC", "Microsoft YaHei", sans-serif;
    background: radial-gradient(1200px 600px at 10% -10%, rgba(56, 189, 248, 0.25), transparent 60%),
      radial-gradient(800px 500px at 90% 0%, rgba(96, 165, 250, 0.22), transparent 55%),
      radial-gradient(1000px 600px at 50% 100%, rgba(129, 140, 248, 0.18), transparent 60%),
      var(--bg);
    color: var(--text);
  }
  
  .app {
    max-width: 980px;
    margin: 0 auto;
    padding: 32px 20px 48px;
  }
  
  header {
    margin-bottom: 24px;
  }
  
  h1 {
    margin: 0 0 8px;
    font-size: 30px;
    font-weight: 700;
    letter-spacing: 0.2px;
    background: linear-gradient(90deg, #e2e8f0, #7dd3fc);
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
  }
  
  .subtitle {
    margin: 0;
    color: var(--muted);
  }
  
  .grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 20px;
  }
  
  .card {
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: 16px;
    padding: 22px;
    box-shadow: var(--glow);
    backdrop-filter: blur(16px);
  }
  
  .form {
    display: grid;
    gap: 14px;
  }
  
  label {
    display: grid;
    gap: 6px;
    font-size: 14px;
    color: var(--muted);
  }
  
.segmented {
  display: grid;
  grid-template-columns: repeat(7, minmax(0, 1fr));
  gap: 8px;
}

.seg-btn {
  height: 42px;
  border-radius: 10px;
  border: 1px solid rgba(148, 163, 184, 0.25);
  background: rgba(15, 23, 42, 0.6);
  color: #e2e8f0;
  font-size: 14px;
  font-weight: 700;
  cursor: pointer;
  box-shadow: inset 0 0 0 1px rgba(30, 41, 59, 0.4);
  transition: border-color 120ms ease, box-shadow 120ms ease, color 120ms ease;
}

.seg-btn:hover {
  border-color: rgba(96, 165, 250, 0.6);
}

.seg-btn.is-active {
  border-color: rgba(96, 165, 250, 0.95);
  color: #e0f2fe;
  box-shadow: 0 0 0 1px rgba(96, 165, 250, 0.4), 0 8px 18px rgba(14, 165, 233, 0.2);
}

.segmented[data-sign="positive"] .seg-btn.is-active {
  border-color: rgba(34, 197, 94, 0.9);
  color: #dcfce7;
  box-shadow: 0 0 0 1px rgba(34, 197, 94, 0.45), 0 8px 18px rgba(34, 197, 94, 0.2);
}

.segmented[data-sign="negative"] .seg-btn.is-active {
  border-color: rgba(248, 113, 113, 0.9);
  color: #fee2e2;
  box-shadow: 0 0 0 1px rgba(248, 113, 113, 0.45), 0 8px 18px rgba(248, 113, 113, 0.2);
}

.segmented[data-sign="zero"] .seg-btn.is-active {
  border-color: rgba(148, 163, 184, 0.9);
  color: #e2e8f0;
  box-shadow: 0 0 0 1px rgba(148, 163, 184, 0.4), 0 8px 18px rgba(148, 163, 184, 0.18);
}

  input {
    padding: 11px 12px;
    border-radius: 10px;
    border: 1px solid rgba(148, 163, 184, 0.25);
    font-size: 16px;
    color: var(--text);
    background: rgba(15, 23, 42, 0.6);
    box-shadow: inset 0 0 0 1px rgba(30, 41, 59, 0.4);
  }
  
  input:focus {
    outline: 2px solid rgba(96, 165, 250, 0.4);
    border-color: rgba(96, 165, 250, 0.8);
  }
  
  .hint {
    margin-top: 16px;
    font-size: 13px;
    color: var(--muted);
    line-height: 1.6;
  }
  
  .results {
    display: grid;
    gap: 12px;
  }
  
  .result {
    display: flex;
    flex-direction: column;
    gap: 6px;
    padding: 14px;
    border-radius: 12px;
    border: 1px solid rgba(148, 163, 184, 0.18);
    background: rgba(15, 23, 42, 0.55);
  }
  
  .label {
    font-size: 13px;
    color: var(--muted);
  }
  
  .value {
    font-size: 22px;
    font-weight: 700;
    color: #e2e8f0;
  }
  
  .error {
    margin-bottom: 16px;
    padding: 10px 12px;
    border-radius: 8px;
    background: rgba(248, 113, 113, 0.12);
    color: var(--danger);
    border: 1px solid rgba(248, 113, 113, 0.35);
    font-size: 14px;
  }
  
  .hidden {
    display: none;
  }
  
  footer {
    margin-top: 24px;
    color: var(--muted);
    font-size: 13px;
    text-align: center;
  }