body {
    display: flex;
    flex-direction: column;
    align-items: center;
}

#light1 {
    width: 100px;
    height: 300px;
    padding: 10px;
    border-radius: 40px;
    display: flex;
    flex-direction: column;
    background-color: black;
    margin: 10px;
}

#light2{
    width: 100px;
    height: 200px;
    padding: 10px;
    border-radius: 40px;
    display: flex;
    flex-direction: column;
    background-color: black;
    margin: 10px;
}

.red {
    width: 100px;
    height: 100px;
    border-radius: 50%;
    background-color: red;
    visibility: visible;
}

.yellow {
    width: 100px;
    height: 100px;
    border-radius: 50%;
    background-color: yellow;
    visibility: hidden;
}

.green {
    width: 100px;
    height: 100px;
    border-radius: 50%;
    background-color: green;
    visibility: hidden;
}

.btn {
    background-color: coral;
    border-radius: 50%;
    width: 100px;
    height: 100px;
    display: flex;
    text-transform: uppercase;
    justify-content: center;
    align-items: center;
    border: 1px solid black;
    margin: 20px;
}