#keys{
    display: grid;

grid-template-columns: repeat(4 , 1fr);
gap: 10px;
padding: 25px;
}
button{
    width: 100px;
    height: 100px;
    border-radius: 50px;
    border: none;
    background-color: black;
    color: white;
    font-size: 3rem;
    font-weight: bold;
    cursor: pointer;

}
#calculator{
    font-family: Arial, sans-serif;
    background-color: black;
    border-radius: 15px;
    max-width: 500px;
    overflow: hidden;
}
#display{
    width: 100%;
    padding: 20px;
    font-size: 5rem;
    text-align: left;
    background-color: black;
    color: white;
}
button:hover{
    background-color: white;
    color: blue;
}
#operator-btn{
    background-color: blue;
}
#operator-btn:hover{
    background-color: purple;
    color: purple;
}
#number-btn{
    background-color: red;
}
#number-btn:hover{
    background-color: white;
    color: green;
}
#clear-btn{
    background-color: green;
}
#clear-btn:hover{
    background-color: white;
    color: green;
}
#equals-btn{
    background-color: yellow;
}
#equals-btn:hover{
    background-color: white;
    color: yellow;
}