styles.css

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

body {
    display: flex;
    align-items: center;
    min-height: 100vh;
    background: linear-gradient(90deg, #bdc3c7 0%, #2c3e50 100%);
}

.container {
    background: linear-gradient(to top, #ffd89b 0%, #19547b 100%);
    width: 300px;
    height: 500px;
    margin: auto;
    justify-content: center;
    border-radius: 12px;
}

.display {
    background-color: black;
    color: white;
    border: none;
    border-radius: 12px 12px 0 0 ;
    height: 120px;
    text-align: right;
    font-size: 1.5rem;
}

button
{
    flex: 0 0 22%;
    width: 60px;
    height: 50px;
    margin: 5px 0;
    font-size: 1.5rem;
    font-weight: 600;
    border: 1px solid black;
    border-radius: 10px;
}

.buttons {
    display: flex;
    flex-wrap: wrap;
    padding: 20px;
    justify-content: space-between;
}

.hidden {
    visibility: hidden;
}