<input type="radio" name="section" id="radio-section-0" checked />
<input type="radio" name="section" id="radio-section-1" />
<input type="radio" name="section" id="radio-section-2" />

<section id="section-0">
  <h2><label for="radio-section-0">Introduction</label></h2>
  <div>
    Content for the introduction.
  </div>
</section>
<section id="section-1">
  <h2><label for="radio-section-1">Previous Experience</label></h2>
  <div>
    Content for the Previous Experiences.
  </div>
</section>
<section id="section-2">
  <h2><label for="radio-section-2">Side Projects</label></h2>
  <div>
    Content for the side projects.
  </div>
</section>
input {
  display: none;
}

section > div {
  display: none;
}

#radio-section-0:checked ~ #section-0 > div {
  display: block;
}

#radio-section-1:checked ~ #section-1 > div {
  display: block;
}

#radio-section-2:checked ~ #section-2 > div {
  display: block;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.