<div class="container">
  <h2>Safe or Unsafe</h2>
  <ul class="wrapper flex">
    <li>CSS</li>
    <li>JavaScript</li>
    <li>CSS: Box Alignment(safe or unsafe)</li>
    <li>React</li>
    <li>Vue</li>
  </ul>
</div>

<form>
  <h2>请选择safe或unsafe</h2>
  <div class="control">
    <label for="safe">Safe or Unsafe:</label>
    <select id="safe">
      <option value="safe">safe</option>
      <option value="unsafe">unsafe</option>
    </select>
  </div>  
</form>  
@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;
    align-items: center;
    justify-content: center;
    flex-wrap: wrap;
    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;
    background-blend-mode: multiply,screen, overlay;
    color: #fff;
}

h2{
  font-size: 2rem;
  text-align: center;
  text-shadow: .05em .05em .01em rgba(0,0,0,.5);
  margin-bottom: 2rem;
}

.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: 1vw;
    color: #fff;
}

.wrapper {
  list-style: none outside none;
  position: relative;
  margin: 0;
  padding: 0;
  border: 1px solid currentColor;
  border-radius: 0.5em;
  color: rgb(71, 73, 84);
  width: 10vw;
  display: flex;
  flex-direction: column;
  
  
  li {
    list-style: none;
    padding: 1em;
    background: #fff;
    border: 1px solid currentColor;
    margin: 5px;
    border-radius: 5px;
    white-space: nowrap;
  }
  
  li + li {
    border-top: 1px solid currentColor;
  }
}



form {
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  font-size: 14px;
  padding: 2vh;
  background: rgba(0,0,0,.8);
  
  h2 {
    font-size: 14px;
    margin-bottom: 3vh;
  }
  
  .control {
    display: grid;
    grid-template-columns: auto 1fr;
    margin-bottom: 10px;
    place-items: center;
    text-align: right;
    gap: 10px;
  }
  
  p {
    position: absolute;
    bottom: 10px;
    right: 10px;
    left: 10px;
    font-size: 12px;
    text-align: center;
  }
}

:root {
  --safe: safe;
}

.wrapper{
  align-items: var(--safe) center;
}
View Compiled
const safeSelector = document.querySelector('#safe')

safeSelector.addEventListener('change', e => {
  document.documentElement.style.setProperty('--safe', e.target.value)
})

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

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