Use CSS to “click” to show hidden effects

CSS implementation click down, see the title oh, click down. Not hover dropdown.

<style lang="">
    ul>li>ul{
      display: none;
    }
    input[type=checkbox]{
      display: none;
    }
    ul li input[type=checkbox]:checked+ul{
      display: block;
    }
 </style>
 <ul>
    <li>
      <label for="checkbox1"> select a </label> <inputtype="checkbox" id='checkbox1' checked="true"> < ul > < li > select a - 1 < / li > < li > select a - 2 < / li > < li > choose one - 3 < / li > < / ul > < / li > < li > < labelfor="checkbox2"> Select two </label> <inputtype="checkbox" id='checkbox2'> < ul > < li > select 2-1 < / li > < li > select 2-2 < / li > < li > select 2-3 < / li > < / ul > < / li > < li > < labelfor="checkbox3"> Select three </label> <inputtype="checkbox" id='checkbox3'> < ul > < li > choose 3-1 < / li > < li > choose 3-2 < / li > < li > select three - 3 < / li > < / ul > < / li > < / ul >Copy the code