:root {
    --accent: #DE0101;
    --text-main: #1a1a1a;
    --text-muted: #6b6b6b;
    --bg-page: #f7f7f8;
    --card-shadow: 0 0 1em 0 #e2e2e2;
  }

  * { box-sizing: border-box; }



  .calc-card {
    max-width: 640px;
    margin: 0 auto;
    background: #fff;
    border-radius: 0.5em;
    box-shadow: var(--card-shadow);
    padding: 28px 24px;
  }

  .subtitle {
    color: var(--text-muted);
    font-size: 14px;
    margin: 0 0 24px;
    line-height: 1.5;
  }

  .tabs {
    display: flex;
    gap: 8px;
    margin-bottom: 20px;
  }

  .tab-btn {
    flex: 1;
    padding: 10px 12px;
    border: 1px solid #e2e2e2;
    background: #fff;
    border-radius: 3px;
    font-family: 'Montserrat', sans-serif;
    font-weight: 600;
    font-size: 14px;
    cursor: pointer;
    color: var(--text-muted);
    transition: all 0.15s ease;
  }

  .tab-btn.active {
    background: var(--accent);
    border-color: var(--accent);
    color: #fff;
  }

  .field {
    margin-bottom: 16px;
  }

  .field label {
    display: block;
    font-size: 13px;
    font-weight: 600;
    margin-bottom: 6px;
    color: var(--text-main);
  }

  .field-row {
    display: flex;
    gap: 12px;
  }

  .field-row .field {
    flex: 1;
  }

  input[type="number"] {
    width: 100%;
    padding: 11px 12px;
    border: 1px solid #d9d9d9;
    border-radius: 3px;
    font-family: 'Montserrat', sans-serif;
    font-size: 15px;
    color: var(--text-main);
    outline: none;
    transition: border-color 0.15s ease;
  }

  input[type="number"]:focus {
    border-color: var(--accent);
  }

  .shape-toggle {
    display: none;
  }
  .shape-toggle.active {
    display: block;
  }

  .result {
    margin-top: 20px;
    padding: 18px;
    border-radius: 0.5em;
    background: #fafafa;
    border: 1px solid #ececec;
  }

  .result-row {
    display: flex;
    justify-content: space-between;
    align-items: baseline;
    margin-bottom: 10px;
  }

  .result-row:last-child { margin-bottom: 0; }

  .result-label {
    font-size: 13px;
    color: var(--text-muted);
  }

  .result-value {
    font-size: 22px;
    font-weight: 700;
  }

  .result-value.small {
    font-size: 15px;
    font-weight: 600;
  }

  .badge {
    display: inline-block;
    padding: 4px 12px;
    border-radius: 20px;
    font-size: 12px;
    font-weight: 600;
    margin-top: 4px;
  }

  .badge-quiet { background: #e6f7ec; color: #1a7d3f; }
  .badge-ok { background: #fff4de; color: #9a6b00; }
  .badge-loud { background: #ffe9e9; color: var(--accent); }

  .hint {
    font-size: 12px;
    color: var(--text-muted);
    margin-top: 12px;
    line-height: 1.5;
  }

  .cta {
    margin-top: 20px;
    text-align: center;
  }

  .cta a {
    display: inline-block;
    background: var(--accent);
    color: #fff;
    text-decoration: none;
    padding: 12px 28px;
    border-radius: 3px;
    font-weight: 600;
    font-size: 14px;
  }

  .placeholder-msg {
    text-align: center;
    color: var(--text-muted);
    font-size: 14px;
    padding: 8px 0 0;
  }