.calculator {
    max-width: 300px;
    margin: 50px auto;
    background-color: #f1f1f1;
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
}

.calculator-screen {
    width: 100%;
    height: 60px;
    font-size: 2rem;
    text-align: right;
    border: none;
    outline: none;
    padding: 0 20px;
    background: white;
}

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

button {
    width: 100%;
    height: 60px;
    font-size: 1.8rem;
    border: none;
    outline: none;
    cursor: pointer;
    background-color: #e0e0e0;
    transition: background-color 0.3s;
}

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

.equal-sign {
    grid-column: span 2;
}

.clear {
    grid-column: span 2;
}

.operator {
    background-color: #f0ad4e;
    color: white;
}

.operator:hover {
    background-color: #ec971f;
}

.decimal {
    background-color: #5bc0de;
    color: white;
}