style.css

a {
    color: #11998e;
    text-decoration: underline;
}

.github-corner:hover .octo-arm {
    animation: octocat-wave 560ms ease-in-out
}

@keyframes octocat-wave {
    0%, 100% {
        transform: rotate(0)
    }
    20%, 60% {
        transform: rotate(-25deg)
    }
    40%, 80% {
        transform: rotate(10deg)
    }
}

@media (max-width: 500px) {
    .github-corner:hover .octo-arm {
        animation: none
    }

    .github-corner .octo-arm {
        animation: octocat-wave 560ms ease-in-out
    }
}


.form__group {
    position: relative;
    padding: 15px 0 0;
    margin-top: 10px;
    width: 50%;
}

.form__field {
    font-family: inherit;
    width: 100%;
    border: 0;
    border-bottom: 2px solid #9b9b9b;
    outline: 0;
    font-size: 1.3rem;
    color: #fff;
    padding: 7px 0;
    background: transparent;
    transition: border-color 0.2s;
}

.form__field::placeholder {
    color: transparent;
}

.form__field:placeholder-shown ~ .form__label {
    font-size: 1.3rem;
    cursor: text;
    top: 20px;
}

.form__label {
    position: absolute;
    top: 0;
    display: block;
    transition: 0.2s;
    font-size: 1rem;
    color: #9b9b9b;
}

.form__field:focus {
    padding-bottom: 6px;
    font-weight: 700;
    border-width: 3px;
    border-image: linear-gradient(to right, #11998e, #38ef7d);
    border-image-slice: 1;
}

.form__field:focus ~ .form__label {
    position: absolute;
    top: 0;
    display: block;
    transition: 0.2s;
    font-size: 1rem;
    color: #11998e;
    font-weight: 700;
}

/* reset input */
.form__field:required, .form__field:invalid {
    box-shadow: none;
}

/* demo */
body {
    font-family: "Poppins", sans-serif;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    font-size: 1.5rem;
    background-color: #222222;
    background-image: radial-gradient(rgba(11, 99, 83, 0.3), rgba(22, 22, 22, 1));
}

.button-33 {
    background-color: #c2fbd7;
    border-radius: 100px;
    box-shadow: rgba(44, 187, 99, .1) 0 -25px 18px -14px inset, rgba(44, 187, 99, .05) 0 1px 2px, rgba(44, 187, 99, .1) 0 2px 4px, rgba(44, 187, 99, .05) 0 4px 8px, rgba(44, 187, 99, .1) 0 8px 16px, rgba(44, 187, 99, .1) 0 16px 32px;
    color: green;
    cursor: pointer;
    display: inline-block;
    font-family: CerebriSans-Regular, -apple-system, system-ui, Roboto, sans-serif;
    padding: 7px 20px;
    text-align: center;
    text-decoration: none;
    transition: all 250ms;
    border: 0;
    font-size: 16px;
    user-select: none;
    -webkit-user-select: none;
    touch-action: manipulation;
}

.button-33:hover {
    box-shadow: rgba(44, 187, 99, .35) 0 -25px 18px -14px inset, rgba(44, 187, 99, .25) 0 1px 2px, rgba(44, 187, 99, .25) 0 2px 4px, rgba(44, 187, 99, .25) 0 4px 8px, rgba(44, 187, 99, .25) 0 8px 16px, rgba(44, 187, 99, .25) 0 16px 32px;
    transform: scale(1.05) rotate(-1deg);
}