JSFiddle - React, Tailwind, and code Playground

HTML

<div class="main_screen_box">
  <div class="title_box">
    <span>TITLE</span>
  </div>
  <div class="main_box">
    <div class="top_header_box">
      <div class="top_header_left_box">
        <span><a>Welcome anonymous</a></span>
      </div>
      <div class="top_header_center_box">
        <span><a href="#" class="button">Register</a></span>
      </div>
      <div class="top_header_right_box">
        <span><a >Login input here</a></span>
      </div>
    </div>
    <div class="center_top_box">
      <div class="error_box">
    </div>
  </div>
  <div class="empety_space_box">
  </div>
  <div class="register_box">
    <form method="register">
      <span><a>Register form</a></span><br>
      <span><a>Name</a></span><br>
      <input type="text" name="name" /><br>
      <span><a>Choose a password</a></span><br>
			<input type="password" name="pass" /><br>
			<button type="submit" name="btn-login">Login</button>
		</form>
	</div>
	<div class="welcome_box">
	   <span><a>Welcome part, bla bla bla bla</a></span>
  </div>
</div>

CSS

html, body {
  height: 100%;
  margin: 0;
  background: #000;
  color: white;
}

.main_screen_box {
  height: 100%;
  padding: 0;
  margin: 0;
  display: flex;
  align-items: center;
  justify-content: space-around;
  box-sizing: border-box;
  flex-direction: column;
}

.title_box {
  display: flex;
  font-size: xx-large;
}

.main_box {
  display: block;
  width: 75%;
  height: 75%;
  border: 2px solid gray;
}

.top_header_box {
  display: flex;
  justify-content: space-between;
  border: 1px solid gray;
  width: 100%;
  height: 35px;
}

.top_header_left_box {
  box-sizing: border-box;
  border: 1px solid gray;
  text-align: left;
  width: 250px;
  height: 100%;
}

.top_header_center_box {
  box-sizing: border-box;
  border: 1px solid gray;
  text-align: center;
  width: 150px;
  height: 100%;
}

.button {
  background-color: black;
  border: none;
  color: white;
  text-align: center;
  text-decoration: none;
  font-size: 16px;
}

.top_header_right_box {
  box-sizing: border-box;
  border: 1px solid gray;
  text-align: right;
  width: 350px;
  height: 100%;
}

.center_top_box {
  display: flex;
  box-sizing: border-box;
  justify-content: center;
  border: 1px solid red;
  width: 100%;
  height: 35px;
}

.error_box {
  display: flex;
  box-sizing: border-box;
  justify-content: center;
  border: 1px solid blue;
  width: 100%;
  height: 35px;
  color: red;
}

.empety_space_box {
  display: flex;
  box-sizing: border-box;
  justify-content: center;
  border: 1px solid blue;
  width: 100%;
  height: 35px;
}

.register_box {
  display: none;
  box-sizing: border-box;
  justify-content: center;
  align-items: center;
  border: 1px solid blue;
  width: 100%;
  height: 200px;
}

.welcome_box {
  display: flex;
  box-sizing: border-box;
  justify-content: center;
  align-items: center;
  border: 1px solid blue;
  width: 100%;
  height: 200px;
}

*:focus ~ .register_box {
  display: flex;
}

*:focus ~ .welcome_box {
  display: none;
}