html {
  height: 100%;
}
body {
  margin: 0;
  padding: 0;
  font-family: sans-serif;
  background: linear-gradient(#141e30, #243b55);
}
.login {
  position: absolute;
  top: 25%;
  left: 40%;
  width: 400px;
  padding: 30px;
  transform: translate(-50%, -50%);
  background: rgba(0, 0, 0, 0.5);
  box-sizing: border-box;
  box-shadow: 0 15px 25px rgba(0, 0, 0, 0.6);
  border-radius: 10px;
}
.login h2 {
  margin: 0 0 30px;
  padding: 0;
  color: #fff;
  text-align: center;
}
.login .user {
  position: relative;
}
.login .user 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;
}
.login .user label {
  position: absolute;
  top: 0;
  left: 0;
  padding: 10px 0;
  font-size: 16px;
  color: #fff;
  pointer-events: none;
  transition: 0.5s;
}
.login .user input:focus ~ label,
.login .user input:valid ~ label {
  top: -30px;
  left: 0;
  color: #03e9f4;
  font-size: 12px;
}