<div id="wrap">

    <div class="logo">
      <span>This is SPARTA!</span>
    </div>
    
    <button id="load"><span>Load!</span></button>

  </div>

//  autoprefixer: true

html,
body {
  width: 100%;
  height: 100%;
  margin: 0;
  padding: 0;
  background-color: #fff;
  color: #fff;
  font-size: 18px;
  font-family: 'Open Sans', sans-serif;
}

*,
*::before,
*::after {
  box-sizing: border-box;
  outline: none;
}

#wrap {
  width: 100%;
  height: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.logo {
  font-size: 60px;
  color: #ccc;
  font-weight: 700;
  position: relative;
  white-space: nowrap;
  
  &::before {
    display: block;
    position: absolute;
    top: 0;
    left: 0;
    width: 0;
    height: 100%;
    content: 'This is SPARTA!';
    color: #000;
    overflow: hidden;
    transition: width 2s ease;
  }
  
  &--loaded {
    &::before {
      width: 100%;  
    }
  }
}

#load {
  width: 200px;
  padding: 10px;
  font-size: 20px;
  margin: 60px auto 0;
}

$(function() {
  $('#load').click(function() {
    $('.logo').addClass('logo--loaded');
  });
});