style.css

body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    background-color: #2f3640;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

.calculator {
    width: 340px;
    background-color: #353b48;
    border-radius: 8px;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.4);
    color: white;
    overflow: hidden;
}

.display {
    background-color: #414b5a;
    border-radius: 8px 8px 0 0;
    padding: 15px 20px;
    text-align: right;
    font-size: 32px;
}

.display input {
    width: 100%;
    background-color: transparent;
    border: none;
    color: white;
}

.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    padding: 20px;
}

button {
    background-color: #596275;
    border: none;
    border-radius: 4px;
    padding: 15px 0;
    font-size: 24px;
    color: white;
    cursor: pointer;
    transition: background-color 0.2s, color 0.2s;
}

button:hover {
    background-color: #4a5463;
}

button.operator {
    background-color: #e74c3c;
}

button.operator:hover {
    background-color: #c0392b;
}

button.equal {
    background-color: #27ae60;
}

button.equal:hover {
    background-color: #219651;
}