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

body {
    background-image: radial-gradient(red, yellow);
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}

.calculator {
    width: 250px;
    background-color: white;
    padding: 2rem;
    border-radius: 1rem;
    box-shadow: 0 0 10px blue;
    text-align: center;
}

#display {
    width: 100%;
    text-align: right;
    padding: 0.4rem;
    border: none;
    outline: none;
    margin-bottom: 1rem;
    font-size: 1.4rem;
}

.btn {
    display: grid;
    grid-template-columns: repeat(4,1fr);
    gap: 0.5rem;
}

button {
    border: none;
    padding: 0.5rem;
    border-radius: 50%;
    background-color: rgb(210, 210, 210);
    width: 100%;
    cursor: pointer;
}

.operator {
    background-color: orange;
    color: #fff;
}

.clear {
    background-color: red;
    color: #fff;
}

.equal {
    background-color: green;
    color: #fff;
}