body{
margin: 0;
padding: 0;
font-family: sans-serif;
background-repeat: no-repeat;
background-size: cover;
background: linear-gradient(120deg, #007bff, #d0314c);
height: 100vh;
overflow: hidden;
}

.center{
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 29vh;
background: #ffff;
border-radius: 10px;
}

.center h1{
    text-align: center;
    padding: 0 0 20px 0;
    border-bottom: 1px solid silver;
}


.center form{
    padding: 0 40px;
    box-sizing: border-box;
}

form .txt_field{
    position: relative;
    border-bottom: 2px solid #adadad;
    margin: 30px 0;
}


.txt_field input{
    width: 100%;
    padding: 0 5px;
    height: 40px;
    font-size: 16px;
    border: none;
    background: none;
    outline: none;
}

.txt_field label{
position: absolute;
top: 50%;
left: 5px;
color: #adadad;
transform: translateY(-50%);
font-size: 16px;
pointer-events: none;
}

.txt_field span::before{
    content:'';
    position: absolute;
    top: 40px;
    left: 0;
    width: 0;
    height: 2px;
    background:#2691d9;
transition:.5s;

}

.txt_field input:focus ~ label, 
.txt_field input:valid ~ label{
    top: -5px;
    color: #2691d9;
}

.txt_field input:focus ~ span, 
.txt_field input:valid ~ span::before{
width: 100%;
}

input[type="Submit"]{
    width: 100%;
    height: 50%;
    border: 1px solid;
    border-radius: 25px;
    font-size: 18px;
    font-weight: 700;
    cursor: pointer;
}


input[type="Submit"]:hover{
    background: #2691d9;
    color: #e9f4fbfb;
    transition: .5s;
}

.signup_link{
    margin: 30px 0;
    text-align: center;
    font-size: 16px;
    color: #6666;
}

.signup_link a{
color: #2691d9;
text-decoration: none;

}

.signup_link a:hover{
    text-decoration: underline;
}





/* y = vertical 
x = h */

/* absolute = tag absolute for containing block */

/* vh = viewport */

/* # = id
. = class */