.keypad {
      display: grid;
      grid-template-columns: repeat(5, minmax(0, 1fr));
      gap: 6px;
      width: 100%;
      max-width: 620px;
      margin: 0 auto;
    }

    .key {
      height: 62px;
      border: 1px solid rgba(255,255,255,0.05);
      border-radius: 12px;
      font-size: 1.2rem;
      font-weight: 700;
      cursor: pointer;
      transition: transform 0.18s ease, box-shadow 0.2s ease, border-color 0.2s ease;
      color: var(--text);
      background: linear-gradient(180deg, rgba(255,255,255,0.10), rgba(255,255,255,0.02));
      box-shadow: inset 0 1px 0 rgba(255,255,255,0.06), 0 8px 18px rgba(0,0,0,0.18);
    }

    .key[data-action="digit"] {
      font-size: 1.42rem;
      font-weight: 800;
    }

    .key[data-action="operator"],
    .key[data-action="decimal"],
    .key[data-action="equals"],
    .key[data-action="toggle-sign"],
    .key[data-action="percent"] {
      font-size: 1.38rem;
      font-weight: 800;
    }

    .key:hover {
      transform: translateY(-2px);
      border-color: rgba(123, 215, 255, 0.38);
      box-shadow: 0 12px 22px rgba(0,0,0,0.24), 0 0 18px rgba(123, 215, 255, 0.10);
    }

    .key.operator {
      background: linear-gradient(135deg, rgba(139, 125, 255, 0.42), rgba(123, 215, 255, 0.14));
      color: #ffffff;
      box-shadow: inset 0 1px 0 rgba(255,255,255,0.08), 0 10px 20px rgba(139, 125, 255, 0.18);
    }

    body.light-mode .key {
      color: #17273d;
    }

    body.light-mode .key.operator {
      color: #1a2540;
    }

    body.light-mode .key.utility {
      color: #1b2330;
    }

    .key.operator[data-value="-"] {
      font-size: 1.75rem;
      font-weight: 900;
      letter-spacing: 0.02em;
      line-height: 1;
    }

    .key.operator[data-value="*"] {
      font-size: 1.65rem;
      font-weight: 900;
      line-height: 1;
    }

    .key.utility {
      background: linear-gradient(135deg, rgba(255, 197, 123, 0.22), rgba(255, 126, 182, 0.18));
      color: #fff9ef;
      box-shadow: inset 0 1px 0 rgba(255,255,255,0.06), 0 8px 18px rgba(255, 143, 189, 0.08);
    }

    .key.utility,
    .key.percent,
    .key.danger {
      font-size: 1.12rem;
    }

    .key[data-action="angle-mode"] {
      font-size: 0.82rem;
      letter-spacing: 0;
      padding: 0 2px;
      white-space: nowrap;
    }

    .angle-mode-label {
      display: inline-flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      line-height: 0.95;
      gap: 2px;
      white-space: nowrap;
    }

    .key.danger {
      background: linear-gradient(135deg, rgba(255, 82, 106, 0.78), rgba(190, 35, 72, 0.82));
      border-color: rgba(255, 145, 158, 0.48);
      color: #ffffff;
    }

    .key.percent {
      background: linear-gradient(135deg, rgba(52, 211, 153, 0.78), rgba(16, 145, 104, 0.84));
      border-color: rgba(118, 255, 202, 0.48);
      color: #effff8;
    }

    .key.primary {
      background: linear-gradient(135deg, #9ef3ff, #b8b2ff 42%, #ffdca1);
      color: #091725;
      font-size: 1.3rem;
      box-shadow: 0 12px 24px rgba(143, 227, 255, 0.24);
    }

    .converter-btn,
    .special-btn,
    .mini-btn {
      font-size: 1.08rem;
    }

    .key.wide {
      grid-column: span 2;
    }

    .is-updated {
      animation: value-pulse 220ms ease;
    }

    @keyframes value-pulse {
      0% { opacity: 0.55; transform: translateY(2px); }
      100% { opacity: 1; transform: translateY(0); }
    }

    .function-row {
      grid-column: 1 / -1;
      display: grid;
      grid-template-columns: repeat(5, minmax(0, 1fr));
      gap: 6px;
    }

    @media (min-width: 640px) {
      body {
        padding: 10px;
      }

      .calc-app {
        border-radius: 20px;
        padding: 11px;
      }
    }

    @media (min-width: 900px) {
      body {
        align-items: center;
        padding: 14px;
      }

      .calc-app {
        border-radius: 22px;
        padding: 12px;
      }
    }