html {
  height: 100%;
}
body {
  margin:0;
  padding:0;
  font-family: sans-serif;
  background: linear-gradient(#000000, #82b900);
}

.container {
  position: absolute;
  top: 50%;
  left: 50%;
  width: 600px;
  padding: 40px;
  transform: translate(-50%, -50%);
  background: rgba(0,0,0,.5);
  box-sizing: border-box;
  box-shadow: 0 15px 25px rgba(0,0,0,.6);
  border-radius: 10px;
}

.container h1 {
  margin: 0 0 40px;
  text-align: center;
  position: relative;
  padding: 12px;
  color: #000000;
  font-size: 15px;
  text-transform: uppercase;
  letter-spacing: 4px;
  background: #fff;;
  border-radius: 5px;
}

.container .form-group {
  position: relative;
}

.container .form-group input {
  width: 100%;
  padding: 10px 0;
  font-size: 16px;
  color: #fff;
  margin-bottom: 30px;
  border: none;
  border-bottom: 1px solid #fff;
  outline: none;
  background: transparent;
}

.container .form-group label {
  position: absolute;
  top: 0;
  left: 0;
  padding: 10px 0;
  font-size: 16px;
  color: #fff;
  pointer-events: none;
  transition: .5s;
}

.container .form-group input:focus {
  outline: none;
}

.container .form-group input:valid ~ label,
.container .form-group input:focus ~ label {
  top: -20px;
  left: 0;
  color: #82b900;
  font-size: 12px;
}

.container button {
  position: relative;
  display:inline-block;
  padding: 10px 13px;
  color: #000000;
  font-size: 10px;
  text-decoration: none;
  text-transform: uppercase;
  overflow: hidden;
  transition: .5s;
  margin-top: 10px;
  letter-spacing: 4px;
  border-radius: 5px;
  font-weight: bold;
}

.container button:hover {
  background: #82b900;
  color: #fff;
  border-radius: 5px;
  box-shadow: 0 0 5px #f4c803,
              0 0 25px #bd9d0b,
              0 0 50px #f4e403,
              0 0 100px #d5cf1e;
}