body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: #282c34;
    margin: 0;
}

.calculator {
    background-color: #1e1e1e;
    padding: 20px;
    border-radius: 15px;
    box-shadow: 0 0 15px rgba(0,0,0,0.5);
    width: 320px;
}

#display {
    background-color: #333;
    color: white;
    padding: 20px;
    font-size: 2rem;
    text-align: right;
    border-radius: 10px;
    margin-bottom: 10px;
    overflow: hidden;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}

.btn {
    background-color: #444;
    color: white;
    padding: 20px;
    font-size: 1.5rem;
    border: none;
    border-radius: 10px;
    cursor: pointer;
    transition: background-color 0.3s;
}

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

.operator {
    background-color: #1DB954;
}

.operator:hover {
    background-color: #1ed760;
}

#equals {
    background-color: #007bff;
    grid-column: span 2;
}

#clear {
    background-color: #d9534f;
    grid-column: span 2;
}