body {
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: #1E1E2F;
    font-family: Arial, sans-serif;
}

.calculator {
    background: #2E2E3A;
    border-radius: 10px;
    padding: 20px;
    width: 350px;
    box-shadow: 0px 4px 10px rgba(0, 0, 0, 0.3);
}

.display {
    background: #1E1E2F;
    color: #FFFFFF;
    font-size: 2rem;
    text-align: right;
    padding: 15px;
    border-radius: 5px;
    margin-bottom: 15px;
    height: 60px;
    overflow-x: auto;
}

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

.btn {
    background: #007BFF;
    color: #FFFFFF;
    font-size: 1.5rem;
    padding: 15px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    transition: background 0.3s;
}

.btn.operator {
    background: #28A745;
}

.btn.equal {
    background: #FF5733;
    grid-column: span 4;
}

.btn:hover {
    background: #0056B3;
}

.btn.operator:hover {
    background: #1C7D3B;
}

.btn.equal:hover {
    background: #C13C23;
}

.btn.clear {
    background: #FFC107;
}

.btn.clear:hover {
    background: #CC9A06;
}