.input-container {
    position: relative;
    margin: 50px auto;
    width: 80%;
  }
  
  .input-container input {
    font-size: 20px;
    width: 100%;
    border: none;
    border-bottom: 2px solid #ccc;
    padding: 5px 0;
    background-color: transparent;
    outline: none;
  }
  
  .input-container .label {
    position: absolute;
    top: 0;
    left: 0;
    color: #ccc;
    transition: all 0.3s ease;
    pointer-events: none;
  }
  
  .input-container input:focus ~ .label,
  .input-container input:valid ~ .label {
    top: -20px;
    font-size: 16px;
    color: #16653b;
  }
  
  .input-container .underline {
    position: absolute;
    bottom: 0;
    left: 0;
    height: 2px;
    width: 100%;
    background-color: #3ebe7a;
    transform: scaleX(0);
    transition: all 0.3s ease;
  }
  
  .input-container input:focus ~ .underline,
  .input-container input:valid ~ .underline {
    transform: scaleX(1);
  }
  

  .btn-submit {
    font-size: 13px;
    letter-spacing: 2px;
    text-transform: uppercase;
    display: inline-block;
    text-align: center;
    font-weight: bold;
    padding: 0.7em 2em;
    border: 3px solid #3ebe7a;
    border-radius: 10px;
    position: relative;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.16), 0 3px 6px rgba(0, 0, 0, 0.1);
    color: #3ebe7a;
    text-decoration: none;
    transition: 0.3s ease all;
    z-index: 1;
  }
  
  .btn-submit:before {
    transition: 0.5s all ease;
    position: absolute;
    top: 0;
    left: 50%;
    right: 50%;
    bottom: 0;
    opacity: 0;
    content: '';
    background-color: #3ebe7a;
    border-radius: 10px;
    z-index: -1;
  }
  
  .btn-submit:hover, .btn-submit:focus {
    color: white;
    border-radius: 10px;
  }
  
  .btn-submit:hover:before, .btn-submit:focus:before {
    transition: 0.5s all ease;
    left: 0;
    right: 0;
    opacity: 1;
  }
  
  .btn-submit:active {
    transform: scale(0.9);
    border-radius: 10px;
  }

  @media only screen and (max-width: 500px) {

    .input-container {
        position: relative;
        margin: 50px auto;
        width: 100%;
    }

  }

  body {
    text-align: center;
    margin: 0px;
    padding: 0px;
    height: 100%;
    color: #fff;
    font-family: sans-serif;
    background: linear-gradient(-45deg, #28b76b, #549583, #3e7d90);
    background-size: 400% 400%;
    -webkit-animation: Gradient 15s ease infinite;
    -moz-animation: Gradient 15s ease infinite;
    animation: Gradient 15s ease infinite;
}

@-webkit-keyframes Gradient {
    0% {
        background-position: 0% 50%
    }

    50% {
        background-position: 100% 50%
    }

    100% {
        background-position: 0% 50%
    }
}

@-moz-keyframes Gradient {
    0% {
        background-position: 0% 50%
    }

    50% {
        background-position: 100% 50%
    }

    100% {
        background-position: 0% 50%
    }
}

@keyframes Gradient {
    0% {
        background-position: 0% 50%
    }

    50% {
        background-position: 100% 50%
    }

    100% {
        background-position: 0% 50%
    }
}