* {
      box-sizing: border-box;
      font-family: "Segoe UI", sans-serif;
    }

    body {
      min-height: 100vh;
      display: flex;
      justify-content: center;
      align-items: center;
      background: linear-gradient(135deg, #667eea, #764ba2);
    }

    #main {
      width: 360px;
      padding: 20px;
      border-radius: 30px;
      background: rgba(255,255,255,0.15);
      /* backdrop-filter: blur(10px); */
      box-shadow: 0 20px 40px rgba(0,0,0,0.3);
    }

    input {
      width: 100%;
      height: 90px;
      border-radius: 20px;
      border: none;
      padding: 15px;
      font-size: 32px;
      text-align: right;
      background: rgba(255,255,255,0.9);
      margin-bottom: 20px;
      outline: none;
    }

    .numpad {
      display: grid;
      grid-template-columns: repeat(4, 1fr);
      gap: 15px;
    }

    button {
      height: 60px;
      border: none;
      border-radius: 15px;
      font-size: 20px;
      cursor: pointer;
      transition: all 0.2s ease;
    }

    button:active {
      transform: scale(0.95);
    }

    .num {
      background: white;
    }

    .num:hover {
      background: #f1f1f1;
    }

    .operator {
      background: #ffd369;
    }

    .operator:hover {
      background: #ffcc4d;
    }

    .clear {
      background: #ff6b6b;
      color: white;
    }

    .clear:hover {
      background: #ff4b4b;
    }

    .equal {
      grid-column: span 4;
      background: #4cd137;
      color: white;
      font-size: 24px;
    }

    .equal:hover {
      background: #44bd32;
    }
    .delete {
      background: #ffa502;
      color: white;
    }

    .delete:hover {
      background: #ff7f00;
}