<div class="container">
  <h2>默认DOM源</h2>
  <div class="control">
    <button type="button">1</button>
    <button type="button">2</button>
    <button type="button">3</button>
    <button type="button">4</button>
  </div>
  
  <h2>Flexbox中的order改变源排列</h2>
  <div class="control order">
    <button type="button">1</button>
    <button type="button">2</button>
    <button type="button">3</button>
    <button type="button">4</button>
  </div>
</div>

@import 'https://fonts.googleapis.com/css?family=Share+Tech+Mono';

@import 'https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css';

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
    width: 100vw;
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    background-image: url('https://s3-us-west-2.amazonaws.com/s.cdpn.io/1376484/jess-harding-lqT6NAmTaiY-unsplash.jpg'),radial-gradient(#28a3dd, #0d7751);
    background-size: cover;
    background-position: center;
    font-family: "Share Tech Mono", monospace;
    font-size: 2rem;
    background-blend-mode: multiply,screen, overlay;
}

.container {
    position: relative;
    background-size: cover;
    background-position: center;
    backdrop-filter: blur(20px);
    background-color: rgba(255, 255, 255, 0.5);
    border-radius: 5px;
    padding:2vw;
    box-sizing: border-box;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.12), 0 1px 2px rgba(0, 0, 0, 0.24);
    transition: .3s ease;
    margin: 3vw;
    display: flex;
    flex-direction: column;
}

button {
	display: inline-flex;
	font-size: 16px;
	font-weight: 700;
	border-radius: 100%;
	transition: background .3s;
  width: 10vh;
  height: 10vh;
  background: #11a8ab;
  border: none 0;
  color: #fff;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  margin: 2vh;
}


button:focus,
button:active {
    box-shadow: inset 0 0 3px  3px #0a166f;
} 

h2 {
  font-size: 8vh;
  color: #fff;
  text-shadow: 1px 1px 2px rgba(0,0,0,.5);
}

.control {
  margin: 2vh;
  padding: 4vh;
  display: flex;
  align-items: center;
}

.order {
  button:nth-child(2) {
    order: 4;
  }
  
  button:nth-child(3){
    order:1;
  }
}