* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    background-color: lightblue;
}

.calculator {
    width: 300px;
    margin: 50px auto;
    background-color: #fff;
    border-radius: 10px;
    box-shadow: 0px 0px 5px #ddd;
    padding: 20px;
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-template-rows: repeat(5, 1fr);
    gap: 10px;
}

.result {
    grid-column: 1/5;
    grid-row: 1/2;
    padding: 10px;
    border: none;
    border-radius: 5px;
    box-shadow: 0px 0px 5px #ddd;
    font-size: 20px;
    text-align: right;
}

.btn {
    border: none;
    border-radius: 5px;
    color: #fff;
    background-color: #333;
    padding: 10px;
    cursor: pointer;
    box-shadow: 0px 0px 5px #ddd;
    font-size: 20px;
}

.operator {
    background-color: #f0ad4e;
}

.calculate {
    background-color: #5cb85c;
}

.clear {
    background-color: #d9534f;
    grid-column: 3/5;
}

.btn:hover {
    background-color: #444;
}

.btn:active {
    background-color: #000;
}