body {
    font-family: Arial, sans-serif;
    background-color: #f4f4f9;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
}

.calculator {
    width: 300px;
    background: #fff;
    border-radius: 10px;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.2);
    overflow: hidden;
}

.display {
    width: 100%;
    height: 80px;
    background: #6f8f70;
    color: #fff;
    font-size: 2em;
    text-align: right;
    padding: 20px;
    box-sizing: border-box;
    border: none;
}

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

.buttons button {
    height: 60px;
    background: #f0f0f0;
    border: none;
    font-size: 1.5em;
    cursor: pointer;
    transition: background 0.3s ease;
}

.buttons button:hover {
    background: #e0e0e0;
}

.buttons .operator {
    background: #4CAF50;
    color: #fff;
}

.buttons .operator:hover {
    background: #45a049;
}

.buttons .clear {
    background: #f44336;
    color: #fff;
}

.buttons .clear:hover {
    background: #e53935;
}

.buttons .equals {
    background: #2196F3;
    color: #fff;
    grid-column: span 2;
}

.buttons .equals:hover {
    background: #1e88e5;
}