HTML/CSS - make a login form Online Editor and JavaScript Compiler

html

<!--My second creation ☹️
trying to creat a login form .
-->
<!DOCTYPE html>
<html lang="en" dir="ltr">
  <head>
    <meta charset="utf-8">
    <title></title>
    <link rel="stylesheet" href="style.css">
    <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4.1/jquery.min.js" charset="utf-8"></script>
  </head>
  <body>
      <form action="index.html" class="login-form">
        <h1>Login</h1>
        <div class="txtb">
          <input type="text">
          <span data-placeholder="Username"></span>
        </div>
        <div class="txtb">
          <input type="password">
          <span data-placeholder="Password"></span>
        </div>
        <input type="submit" class="logbtn" value="Login">

css

*{
  margin: 0;
  padding: 0;
  text-decoration: none;
  font-family: montserrat;
  box-sizing: border-box;
}
body{
  min-height: 100vh;
  background-image: linear-gradient(120deg,#3498db,#8e44ad);
  
}
.login-form{
  width: 260px;
  background: #f1f1f1;
  height: 480px;
  padding: 80px 40px;
  border-radius: 10px;
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%,-50%);
    background-color:#8bfff4;
}
.login-form h1{

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