<form>
<input id="a" type="radio" name="hopping" value="a" checked>
<label for="a"><span></span>A</label>
<input id="b" type="radio" name="hopping" value="b">
<label for="b"><span></span>B</label>
<input id="c" type="radio" name="hopping" value="c">
<label for="c"><span></span>C</label>
<div class="worm">
<div class="worm__segment"></div>
<div class="worm__segment"></div>
<div class="worm__segment"></div>
<div class="