*{
    box-sizing: border-box;
}
body{
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: hsl(0, 0%, 95%);
}
#Calculator{
    font-family: Arial, sans-serif;
    background-color: hsl(0, 0%, 15%);
    border-radius: 15px;
    max-width: 320px;
    width: 100%;
}
#display{
    width: 100%;
    padding: 15px;
    font-size: 2rem;
    text-align: right;
    border: none;
    background-color: hsl(0, 0%, 20%);
    color: white;
    overflow-x: auto;
    white-space: nowrap;
}
#display::-webkit-scrollbar{
    display: none;
}
#keys{
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 8px;
    padding: 10px;
}
button{
    width: 100%;
    height: 55px;
    border-radius: 50px;
    border: none;
    background-color: hsl(0, 0%, 30%);
    color: white;
    font-size: 1.1rem;
    font-weight: bold;
    cursor: pointer;
}
button:hover{
    background-color: hsl(0, 0%, 40%);
}
button:active{
    background-color: hsl(0, 0%, 50%);
}
.operator-btn{
    background-color: hsl(39, 100%, 55%);
}
.operator-btn:hover{
    background-color: hsl(39, 100%, 65%);
}
.operator-btn:active{
    background-color: hsl(39, 100%, 75%);
}

@media (max-width: 400px){
    #display{
        font-size: 1.8rem;
    }

    button{
        height: 50px;
        font-size: 1rem;
    }
}