* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: Arial, sans-serif;
}

body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color: #f5f5f5;
}

.calculator {
    background-color: #333;
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.3);
    width: 300px;
    overflow: hidden;
}

@media (max-width: 480px) {
    .calculator {
        width: 100%;
        max-width: 400px;
        margin: 10px;
    }

    .display {
        font-size: 1.5rem;
        padding: 15px;
    }

    .btn {
        font-size: 1.2rem;
        padding: 15px;
    }
}

.display {
    background-color: #222;
    color: white;
    text-align: right;
    padding: 20px;
    font-size: 2rem;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 1px;
    background-color: #444;
}

.btn {
    border: none;
    background-color: #555;
    color: white;
    font-size: 1.5rem;
    padding: 20px;
    cursor: pointer;
    transition: background-color 0.2s;
}

.btn:hover {
    background-color: #666;
}

.operator {
    background-color: #ff9500;
}

.operator:hover {
    background-color: #ffaa33;
}

.equals {
    background-color: #ff9500;
    grid-row: span 2;
}


.clear {
    grid-column: span 2;
    background-color: #a5a5a5;
    color: #000;
}

.clear:hover {
    background-color: #b5b5b5;
}

#zero {
    grid-column: span 2;
}