* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: sans-serif;
  }
  
  body {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    background: linear-gradient(#141e30, #243b55);
  }
  
  .login {
    background: rgba(0,0,0,0.5);
    box-shadow: 0 15px 25px rgba(0,0,0,.6);
    border-radius: 10px;
    width: 400px;
    padding: 50px;
    box-sizing: border-box;
  }
  
  h2{
    margin-bottom: 30px;
    font-size: 30px;
    color: #FFF;
    text-align: center;
  }
  
  .box-user{
    position: relative;
  }
  
  input{
    width: 100%;
    padding: 10px 0;
    margin-bottom:30px;
    outline: none;
    border: none;
    background: transparent;
    border-bottom: 1px solid #fff;
    color: #fff;
    font-size: 16px;
  }
  
  label {
    position: absolute;
    top:0;
    left:0;
    padding: 10px 0;
    color: #FFF;
    font-size: 16px;
    pointer-events: none;
    transition: .5s;
  }
  
  input:focus~label,
  input:valid~label
  {
    top: -12px;
    left: 0;
    color: #03e9f4;
    font-size: 12px;
  }
  
  .forget {
    font-size: 12px;
    color: #5B6B8B;
    display: flex;
    justify-content: flex-end;
    margin: 10px 0;
    
  }
  
  .btn{
      position: relative;
      display: inline-block;
      padding: 12px 20px;
      color: #03e9f4;
      text-decoration: none;
      font-size: 13px;
      text-transform: uppercase;
      letter-spacing: 4px;
      font-weight: 700;
      margin-top: 20px;
      transition: .5s;
      overflow: hidden;
  }
  
  .btn:hover{
      background: #03e9f4;
      border-radius: 5px;
      color: #172031;
  }
  .btn span{
      position: absolute;
      display: block;
  }
  .btn span:nth-child(1){
      top: 0;
      left: -100%;
      width: 100%;
      height: 4px;
      background: linear-gradient(90deg, transparent, #03e9f4);
    animation: btn1 1s linear infinite;
  }
  
  @keyframes btn1{
      0%{
          left: -100%;
      }
      50%,
      100%{
          left: 100%;
      }}