<div class="wrapper">
  <input name="rad" class="opt-1" id="rad1" type="radio" />
  <label for="rad1">Hello 😺</label>

  <input name="rad" class="opt-2" id="rad2" type="radio" />
  <label for="rad2">is it kitty 😸</label>

  <input name="rad" class="opt-3" id="rad3" type="radio" />
  <label for="rad3">you're looking for? 😻</label>

  <input name="rad" class="opt-4" id="rad4" type="radio" />
  <label for="rad4">No?? 😿</label>
  <div class="tracker"></div>
</div>
html,
body {
  height: 100%;
}

body {
  padding: 0;
  margin: 0;
  background: #222;
  color: #fff;
}

input {
  opacity: 0;
  width: 0;
  height: 0;
  position: absolute;
}

.wrapper {
  position: absolute;
  padding-bottom: 1.25em;
  width: 100%;
  max-width: 52rem;
  margin: 8rem 0 5rem;
  left: 50%;
  transform: translateX(-50%);
  font-size: 0;
}

label {
  position: relative;
  display: inline-block;
  cursor: pointer;
  width: 140px;
  height: 50px;
  margin-right: 10px;
  line-height: 50px;
  text-align: center;
  font-family: "Courier New", Courier, monospace;
  font-size: 17px;
}

.opt-3 + label {
  width: 300px;
}

/* background-size and backround-position on :checked is only needed if using gradients instead of solid backgrounds  */
.tracker {
  height: 2px;
  width: 140px;
  background: linear-gradient(to right, limegreen, skyblue, darkorchid, hotpink, aqua);
  background-size: 400%;
  position: absolute;
  transition: all 270ms ease-in-out, width 270ms ease-in-out;
}

.opt-2:checked ~ .tracker {
  transform: translateX(0);
}

.opt-2:checked ~ .tracker {
  background-position: 25%;
  transform: translateX(150px);
}

.opt-3:checked ~ .tracker {
  width: 300px;
  background-position: 60%;
  transform: translateX(300px);
}

.opt-4:checked ~ .tracker {
  background-position: 90%;
  transform: translateX(600px);
}

@media screen and (max-width: 770px) {
  .opt-4,
  .opt-4 + label {
    display: none;
  }
}
/*
Thanks to @NeXTs for the trick on how to make the gradients transition smoothly
https://codepen.io/meowwwls/details/EgqWMo#comment-id-161359

Not:
- responsive
- dynamic
- that good

This was just an experiment to see if I could do this without JavaScript


*/

External CSS

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External JavaScript

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