.roman-calc,
    .roman-calc *,
    .roman-calc *::before,
    .roman-calc *::after {
      box-sizing: border-box;
    }

    body {
      margin: 0;
      background: #111827;
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    }

    .roman-calc {
      min-height: 100vh;
      display: flex;
      align-items: center;
      justify-content: center;
      padding: 20px;
      background: radial-gradient(circle at center, #1f2937 0%, #111827 100%);
      user-select: none;
    }

    .calculator {
      width: 100%;
      max-width: 400px;
      background: #000;
      border: 1px solid #374151;
      border-radius: 32px;
      padding: 24px;
      box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.7);
    }

    .display-container {
      min-height: 150px;
      margin-bottom: 20px;
      padding: 28px 24px;
      background: #111827;
      border: 1px solid #1f2937;
      border-radius: 20px;
      display: flex;
      flex-direction: column;
      justify-content: flex-end;
    }

    .history {
      min-height: 24px;
      margin-bottom: 8px;
      text-align: right;
      font-size: 16px;
      color: #9ca3af;
      word-break: break-word;
    }

    .display {
      text-align: right;
      font-size: 44px;
      font-weight: 300;
      color: #fff;
      white-space: nowrap;
      overflow-x: auto;
      scrollbar-width: none;
      letter-spacing: 1px;
    }

    .display::-webkit-scrollbar {
      display: none;
    }

    .buttons {
      display: grid;
      grid-template-columns: repeat(4, 1fr);
      gap: 14px;
    }

    button {
      height: 70px;
      display: flex;
      align-items: center;
      justify-content: center;
      border: none;
      border-radius: 18px;
      cursor: pointer;
      font-size: 22px;
      font-weight: 500;
      color: #fff;
      transition: all 0.1s ease;
    }

    button:active {
      transform: scale(0.92);
    }

    .btn-gray {
      background: #4b5563;
      color: #f3f4f6;
    }

    .btn-gray:hover {
      background: #6b7280;
    }

    .btn-dark {
      background: #1f2937;
    }

    .btn-dark:hover {
      background: #374151;
    }

    .btn-orange {
      background: #f97316;
    }

    .btn-orange:hover {
      background: #fb923c;
    }

    .btn-orange.active {
      background: #fff;
      color: #f97316;
      box-shadow: 0 0 15px rgba(249, 115, 22, 0.4);
    }

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

    .hint {
      margin-top: 15px;
      text-align: center;
      font-size: 11px;
      color: #6b7280;
      text-transform: uppercase;
      letter-spacing: 1px;
      line-height: 1.5;
    }