Custom radio button using CSS only

Custom radio button style using only CSS (SCSS) by taking advantage of sibling selectors and the :checked psuedo class.

See the Pen Pill styled radio buttons | Fully scaleable by Håvard Brynjulfsen (@havardob) on CodePen.

index.html

<div class="container">
<form>
<label>
<input type="radio" name="radio" checked/>
<span>HTML</span>
</label>
<label>
<input type="radio" name="radio"/>
<span>CSS</span>
</label>
<label>
<input type="radio" name="radio"/>
<span>Javascript</span>
</label>
</form>
</div>

*,
*:after,
*:before {
  box-sizing: border-box;
}

body {
  font-family: "Inter", sans-serif;
  color: #000021;
  font-size: calc(1em + 1.25vw);
  background-color: #e6e6ef;
}

form {
  display: -webkit-box;
  display: flex;
  flex-wrap: wrap;
  -webkit-box-orient: vertical;
  -webkit-box-direction: normal;
          flex-direction: column;
}

label {
  display: -webkit-box;
  display: flex;
  cursor: pointer;
  font-weight: 500;
  position: relative;
  overflow: hidden;
  margin-bottom: 0.375em;
  
}
label input {
  position: absolute;
  left: -9999px;
}
label input:checked + span {
  background-color: #d6d6e5;
}
label input:checked + span:before {
  box-shadow: inset 0 0 0 0.4375em #00005c;
}
label span {
  display: -webkit-box;
  display: flex;
  -webkit-box-align: center;
          align-items: center;
  padding: 0.375em 0.75em 0.375em 0.375em;
  border-radius: 99em;
  -webkit-transition: 0.25s ease;
  transition: 0.25s ease;
}
label span:hover {
  background-color: #d6d6e5;
}
label span:before {
  display: -webkit-box;
  display: flex;
  flex-shrink: 0;
  content: "";
  background-color: #fff;
  width: 1.5em;
  height: 1.5em;
  border-radius: 50%;
  margin-right: 0.375em;
  -webkit-transition: 0.25s ease;
  transition: 0.25s ease;
  box-shadow: inset 0 0 0 0.125em #00005c;
}

.container {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  width: 100%;
  display: -webkit-box;
  display: flex;
  -webkit-box-pack: center;
          justify-content: center;
  -webkit-box-align: center;
          align-items: center;
  padding: 20px;
}

*,
*:after,
*:before {
  box-sizing: border-box;
}

body {
  font-family: "Inter", sans-serif;
  color: #000021;
  font-size: calc(1em + 1.25vw);
  background-color: #e6e6ef;
}

form {
  display: -webkit-box;
  display: flex;
  flex-wrap: wrap;
  -webkit-box-orient: vertical;
  -webkit-box-direction: normal;
          flex-direction: column;
}

label {
  display: -webkit-box;
  display: flex;
  cursor: pointer;
  font-weight: 500;
  position: relative;
  overflow: hidden;
  margin-bottom: 0.375em;
  
}
label input {
  position: absolute;
  left: -9999px;
}
label input:checked + span {
  background-color: #d6d6e5;
}
label input:checked + span:before {
  box-shadow: inset 0 0 0 0.4375em #00005c;
}
label span {
  display: -webkit-box;
  display: flex;
  -webkit-box-align: center;
          align-items: center;
  padding: 0.375em 0.75em 0.375em 0.375em;
  border-radius: 99em;
  -webkit-transition: 0.25s ease;
  transition: 0.25s ease;
}
label span:hover {
  background-color: #d6d6e5;
}
label span:before {
  display: -webkit-box;
  display: flex;
  flex-shrink: 0;
  content: "";
  background-color: #fff;
  width: 1.5em;
  height: 1.5em;
  border-radius: 50%;
  margin-right: 0.375em;
  -webkit-transition: 0.25s ease;
  transition: 0.25s ease;
  box-shadow: inset 0 0 0 0.125em #00005c;
}

.container {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  width: 100%;
  display: -webkit-box;
  display: flex;
  -webkit-box-pack: center;
          justify-content: center;
  -webkit-box-align: center;
          align-items: center;
  padding: 20px;
}