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CSS

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HTML 

              
                <body>
  <div class="wrap">
    <div class="menu">
      <ul>
        <li><a href="#">回到首頁</a></li>
        <li><a href="#">關於我們</a></li>
        <li><a href="#">熱銷產品</a></li>
        <li><a href="#">購物車</a></li>
      </ul>
    </div>
    <div class="content">
      Lorem ipsum dolor sit amet consectetur, adipisicing elit. Similique excepturi nisi doloribus sapiente culpa
      dolorem dolores sint, expedita perferendis iure suscipit ut, laudantium animi praesentium dolorum. Esse
      debitis ipsa quam, soluta ex fuga quae iusto doloremque, incidunt, totam minima enim ad aliquam! Fugit
      dolorem maxime, saepe molestias veniam consequatur ut?
      Lorem ipsum dolor sit amet consectetur, adipisicing elit. Similique excepturi nisi doloribus sapiente culpa
      dolorem dolores sint, expedita perferendis iure suscipit ut, laudantium animi praesentium dolorum. Esse
      debitis ipsa quam, soluta ex fuga quae iusto doloremque, incidunt, totam minima enim ad aliquam! Fugit
      dolorem maxime, saepe molestias veniam consequatur ut?
      Lorem ipsum dolor sit amet consectetur, adipisicing elit. Similique excepturi nisi doloribus sapiente culpa
      dolorem dolores sint, expedita perferendis iure suscipit ut, laudantium animi praesentium dolorum. Esse
      debitis ipsa quam, soluta ex fuga quae iusto doloremque, incidunt, totam minima enim ad aliquam! Fugit
    </div>
  </div>
</body>

<div class="container description" style="margin-top: 20px;margin-bottom: 20px;">
  <h2>flex-shrink 計算方式</h2>
  <p>壓縮權重（sum）: shrink * menu_width + shrink * content_width</p>
  <p>以此範例：</p>
  <p>sum = 3 * 300 + 1 * 900 = 1800</p>
  <hr>
  <p>元素壓縮率 (S): shrink * menu_width/壓縮權重(sum)</p>
  <p>以此範例：</p>
  <p>S1 = 3 * 300 / 1800 = 0.5</p>
  <hr>
  <p>元素寬度 (W): menu_width - S*剩餘寬度</p>
  <p>以此範例：</p>
  <p>W = 300 - 0.5*200 = 200</p>
  <p><small>註：剩餘空間是 (300+900) - 1000 算出來的</small></p>
</div>
!

CSS 

              
                .wrap{
  max-width: 1000px;
  margin: 0 auto;
  display: flex;
}
.container {
  max-width: 1000px;
  margin: 0 auto;
}
.menu{
  flex-basis: 300px;
  color: blue;
  background: #000;
  padding-top: 10px;
  flex-shrink: 3;
}



.menu li a {
  display: block;
  text-align: center;
  padding-bottom: 10px;
  color: #fff;
}


.content{
  flex-basis: 900px;
  background: orange;
  color: #fff;
  flex-shrink: 1;
  padding: 10px 0px;
}

.description h2 {
  font-size: 24px;
  line-height: 1.5;
}
.description p {
  line-height: 1.5;
}
!

JS
!
999px

Console