body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: #f4f4f4;
}

.calculator {
    background-color: #fff;
    border-radius: 10px;
    box-shadow: 0 4px 10px rgba(0,0,0,0.1);
    padding: 20px;
    width: 260px;
}

.display {
    width: 100%;
    height: 60px;
    background-color: #222;
    color: #fff;
    text-align: right;
    font-size: 2em;
    padding: 10px;
    border-radius: 5px;
    margin-bottom: 10px;
    overflow: hidden;
}

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

button {
    background-color: #f0f0f0;
    border: none;
    border-radius: 5px;
    font-size: 1.5em;
    padding: 20px;
    cursor: pointer;
    transition: background-color 0.3s;
}

button:hover {
    background-color: #ddd;
}

button.operator {
    background-color: #ff9500;
    color: white;
}

button.operator:hover {
    background-color: #e68900;
}

button.clear {
    background-color: #ff3b30;
    color: white;
}

button.clear:hover {
    background-color: #e32b1f;
}

button.equal {
    background-color: #4cd964;
    color: white;
}

button.equal:hover {
    background-color: #3bbf53;
}