html, body {
    height: 100%;
}
body{
    background: rgb(160 57 225);
    background: linear-gradient(-45deg, rgb(160 57 225), rgb(15, 191, 191), #f11583, #bcf104);
    background-size: 400% 400%;
    animation: gradient 15s ease infinite;
    display: flex;
    align-items: center;
    justify-content: center;
}
@keyframes gradient {
    0% {background-position: 0% 50%;}
    50% {background-position: 100% 50%;}
    100% {background-position: 0% 50%;}
}
#form-code {
    width: auto;
    color: white;
}
#form-code .form-control {
    display: block;
    height: 80px;
    width: 80px;
    margin-right: 10px;
    text-align: center;
    font-size: 50px;
    min-width: 0;
    line-height: 100%;
}
#form-code button {
    font-size: 20px;
    text-transform: uppercase;
}

@media (max-width: 460px) {
    #form-code .form-control {
        height: 55px;
        width: 55px;
        margin-right: 0px;
        font-size: 30px;
    }
}