body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: #f0f2f5;
    margin: 0;
    font-family: sans-serif;
}

.calculator {
    background-color: #333;
    padding: 20px;
    border-radius: 15px;
    box-shadow: 0px 10px 20px rgba(0,0,0,0.2);
    width: 300px;
}

#display {
    width: 100%;
    height: 60px;
    font-size: 32px;
    text-align: right;
    margin-bottom: 20px;
    padding: 10px;
    box-sizing: border-box;
    border: none;
    border-radius: 5px;
    background-color: #eee;
}

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

button {
    padding: 20px;
    font-size: 18px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    background-color: #555;
    color: white;
    transition: 0.2s;
}

button:active {
    background-color: #777;
}

.btn-clear {
    background-color: #ff5252;
}

.btn-equal {
    background-color: #4caf50;
    grid-row: span 2; /* Tombol = memanjang ke bawah */
}

.zero {
    grid-column: span 2; /* Tombol 0 memanjang ke samping */
}