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

body {
    min-height: 100vh;

    display: flex;
    justify-content: center;
    align-items: center;

    background: #111;
    font-family: Arial, sans-serif;
}

.calculator {
    width: 320px;
    padding: 20px;

    background: #222;
    border-radius: 16px;

    box-shadow: 0 20px 50px rgba(0, 0, 0, 0.4);
}

.top-bar {
    display: flex;
    justify-content: flex-end;

    margin-bottom: 12px;
}

#musicButton {
    height: 36px;
    padding: 0 12px;

    border: none;
    border-radius: 8px;

    background: #333;
    color: white;

    font-size: 14px;
    cursor: pointer;
}

#musicButton:hover {
    background: #444;
}

#display {
    width: 100%;
    height: 70px;

    margin-bottom: 15px;
    padding: 10px;

    border: none;
    border-radius: 10px;

    background: #111;
    color: white;

    font-size: 32px;
    text-align: right;
}

.buttons {
    display: grid;

    grid-template-columns: repeat(4, 1fr);

    gap: 10px;
}

button {
    height: 60px;

    border: none;
    border-radius: 10px;

    background: #333;
    color: white;

    font-size: 20px;

    cursor: pointer;

    transition: 0.15s;
}

button:hover {
    background: #444;
    transform: translateY(-2px);
}

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

.operator {
    background: #555;
}

.operator:hover {
    background: #666;
}

.equals {
    background: #777;
}

.equals:hover {
    background: #888;
}

.zero {
    grid-column: span 2;
}