* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Arial', sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}

.calculator-container {
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
    border-radius: 20px;
    padding: 20px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
}

.calculator {
    width: 320px;
    background: #1a1a1a;
    border-radius: 15px;
    overflow: hidden;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
}

.display {
    background: #2d2d2d;
    padding: 20px;
    text-align: right;
    min-height: 100px;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
}

.previous-operand {
    color: #888;
    font-size: 18px;
    margin-bottom: 5px;
    min-height: 25px;
}

.current-operand {
    color: #fff;
    font-size: 36px;
    font-weight: bold;
    overflow: hidden;
    text-overflow: ellipsis;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 1px;
    background: #333;
}

.btn {
    border: none;
    outline: none;
    padding: 25px;
    font-size: 20px;
    font-weight: bold;
    cursor: pointer;
    transition: all 0.2s ease;
    background: #4a4a4a;
    color: #fff;
}

.btn:hover {
    background: #5a5a5a;
    transform: scale(0.98);
}

.btn:active {
    transform: scale(0.95);
}

.btn.clear {
    background: #ff6b6b;
    color: #fff;
}

.btn.clear:hover {
    background: #ff5252;
}

.btn.operator {
    background: #ffa726;
    color: #fff;
}

.btn.operator:hover {
    background: #ff9800;
}

.btn.equals {
    background: #4caf50;
    color: #fff;
    grid-row: span 2;
}

.btn.equals:hover {
    background: #45a049;
}

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

/* レスポンシブデザイン */
@media (max-width: 480px) {
    .calculator {
        width: 280px;
    }
    
    .btn {
        padding: 20px;
        font-size: 18px;
    }
    
    .current-operand {
        font-size: 30px;
    }
}