body{
    margin: 0;
    display:flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: hsl(0, 0%, 100%);
}
#calc{
    font-family: Arial, Helvetica, sans-serif;
    background-color: hsl(0, 0%, 15%);
    border-radius: 20px;
    max-width: 500px;
    overflow: hidden;

}
#Screen{
    width: 92%;
    padding: 20px;
    font-size: 4rem;
    font-family: Arial, Helvetica, sans-serif;
    text-align: left;
    color: white;
    border: none;
    background-color: hsl(0, 0%, 20%);
}
#Keys{
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    font-family: 'Ariel';
    grid-gap: 10px;
    padding: 25px;
    margin-top: 20px;
}
button {
    background-color: #000;
    color: white;
    padding: 20px;
    border: none;
    cursor: pointer;
    font-size: 20px;
    font-weight: bold;
    border-radius: 5px;
    transition: background-color 0.3s;
}
button:hover{
    background-color: hsl(0, 0%, 30%);
}
button:active{
    background-color: hsl(0, 0%, 45%);
}
.operator{
    color: rgb(21, 228, 21);
}
.clear{
    color: red;
}
.del{
    color: rgb(254, 254, 103);
}
.ans{
    color: rgb(0, 170, 255);
}
.on{
    color: white;
}
.off {
    color: white;
}
.on.active{
    color: rgb(170, 9, 170);
}
.off.active {
    color: rgb(170, 9, 170);
}