* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: linear-gradient(135deg, #6e45e2, #88d3ce);
    padding: 20px;
}

.calculator {
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
    border-radius: 20px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3), 
                inset 0 1px 1px rgba(255, 255, 255, 0.2);
    padding: 25px;
    width: 320px;
    border: 1px solid rgba(255, 255, 255, 0.2);
}

.display {
    margin-bottom: 25px;
}

#display {
    width: 100%;
    height: 70px;
    border: none;
    border-radius: 12px;
    background: rgba(255, 255, 255, 0.9);
    font-size: 28px;
    font-weight: 500;
    text-align: right;
    padding: 15px;
    color: #333;
    box-shadow: inset 0 2px 5px rgba(0, 0, 0, 0.1);
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-gap: 12px;
}

.btn {
    height: 60px;
    border: none;
    border-radius: 12px;
    font-size: 20px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

.btn:hover {
    transform: translateY(-3px);
    box-shadow: 0 6px 12px rgba(0, 0, 0, 0.15);
}

.btn:active {
    transform: translateY(1px);
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.number {
    background: linear-gradient(145deg, #3a3a3a, #4d4d4d);
    color: white;
}

.operator {
    background: linear-gradient(145deg, #ff8800, #ff9500);
    color: white;
    font-weight: bold;
}

.clear {
    background: linear-gradient(145deg, #ff2d20, #ff3b30);
    color: white;
    font-weight: bold;
}

#backspace {
    background: linear-gradient(145deg, #ff2d20, #ff3b30);
    color: white;
    font-weight: bold;
}

.equals {
    background: linear-gradient(145deg, #28b348, #34c759);
    color: white;
    grid-row: span 2;
    font-weight: bold;
}

.zero {
    grid-column: span 2;
}

@media (max-width: 350px) {
    .calculator {
        width: 100%;
        padding: 15px;
    }
    
    .btn {
        height: 50px;
        font-size: 18px;
    }
}