style.css

body{
    padding: 0;
    margin: 0;
    height: 100vh;
    width: 100vw;
    display: flex;
    justify-content: center;
    align-items: center;
}
.background{
    height: 300px;
    width: 700px;
    display: flex;
    justify-content: space-around;
    align-items: center;
    border: 5px solid #212121;
    transition: background-color 0.5s ease;
}
.blackbutton{
    height: 100px;
    width: 100px;
    border: 2px solid #212121;
    border-radius: 100%;
    cursor: pointer;
    background-color: black;
    transition: transform 0.2s ease-in-out;
}
.yellowbutton {
    height: 100px;
    width: 100px;
    border: 2px solid #212121;
    border-radius: 100%;
    cursor: pointer;
    background-color: rgb(209, 254, 9);
    transition: transform 0.2s ease-in-out;
}
.redbutton {
    height: 100px;
    width: 100px;
    border: 2px solid #212121;
    border-radius: 100%;
    cursor: pointer;
    background-color: rgb(255, 4, 21);
    transition: transform 0.2s ease-in-out;
}
.blackbutton:hover{
    transform: scale(1.2);
}
.yellowbutton:hover {
    transform: scale(1.2);
}
.redbutton:hover {
    transform: scale(1.2);
}