body{
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
}
#keys{
    display: grid;
    grid-template-columns: auto auto auto auto;
    gap: 10px;
    padding: 25px;
}
button{
    width: 100px;
    height: 100px;
    border-radius: 100px;
    border: none;
    background-color: rgb(70, 70, 70);
    color: white;
    font-size: 67px;
    font-weight: bold;
    cursor: pointer;
}
#bg {
    font-family: Arial, sans-serif;
    background-color: rgb(40, 40, 40);
    border-radius: 15px;
    max-width: 500px;
    overflow: hidden;
}
#display{
    width: 100%;
    font-size: 50px;
    text-align: left;
    border: none;
    color: white;
    background-color: rgb(67, 67, 67);
    padding: 20px;
}
.operator{
    background-color: rgb(255, 166, 0);
}
button:hover{
    background-color: rgb(90, 90, 90);
}
.operator:hover{
    background-color: rgb(255, 193, 78);
}
button:active{
    background-color: rgb(110, 110, 110);
}
.operator:active{
    background-color: rgb(255, 213, 134);
}