body{
    background: linear-gradient(120deg, #2980B9, #8e44a8) no-repeat;
    height: 100vh;
}
head{
    font-family: 'Roboto Slab', serif;
}
.center{
    width: 400px;
    height: 500px;
    background-color: white;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%,-50%);
    border-radius: 10px;
}
.center h1{
    text-align: center;
    padding-bottom: 20px;
    border-bottom: 1px solid silver;
}
.center form{
    padding: 0 40px;
}
form .text-field{
    position: relative;
    border-bottom: 2px solid #adadad;
    margin: 30px 0;
}
.text-field input{
    width: 100%;
    height: 40px;
    font-size: 16px;
    background: none;
    outline: none;
    border: none;
}
.text-field label{
    position: absolute;
    top: 0;
    transform: translateY(70%);
    pointer-events: none;
    font-size: 16px;
    transition: 0.7s;
}
.text-field span{
    position: absolute;
    width: 0%;
    height: 2px;
    background-color: red;
    top: 42px;
    transition: 0.7s;
}
.text-field input:focus ~ label{
    top: -20px;
    color: red;
}
.text-field input:focus ~ span{
    width: 100%;
    background-color: red;
}
.text-field input:valid ~ label{
    top: -20px;
    color: #2980B9;
}
.text-field input:valid ~ span{
    width: 100%;
    background-color: #2980B9;
}
.button{
    background-color: #2691D9;
    border: none;
    border-radius: 109px;
    color: white;
    padding: 10px 130px;
    text-align: center;
    display: inline-block;
    font-size: 16px;
    cursor: pointer;
    text-decoration: none;
}
.button:hover{
    background-color: #2980B9;
}
.signin{
    text-decoration: none;
}