- var letters = [ ["A","B","C","D","E"], ["F","G","H","J","K"] ];
- var groups = 8;
- var itemsPerGroup = 10;
- var itemsInLastGroup = 5;

form(action="")
  - for (g = 0; g < groups; ++g) {
    .bubble-group
      - var ipg = g == groups - 1 ? itemsInLastGroup : itemsPerGroup;
      - for (r = 0; r < ipg; ++r) {
        - var n = r + (itemsPerGroup * g) + 1;
        - var l = letters[r % 2];
        strong=n
        - for (b = 0; b < l.length; ++b) {
          input(type="radio",name="_"+n,id="_"+n+l[b])
          label(for="_"+n+l[b]).bubble
            span.bubble-inner=l[b]
        - }
      - }
  - }
  button(type="submit")="Submit"
View Compiled 
*, *:before, *:after {
  border: 0;
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
:root {
  --c: rgb(32,176,144);
  --c2: rgb(26,130,107);
  font-size: 16px;
}
body, button, input {
  font: 1em "Helvetica Neue", Helvetica, sans-serif;
  line-height: 1.5;
}
body {
  color: rgb(32,176,144);
  color: var(--c);
}
input, button {
  -webkit-appearance: none;
  -moz-appearance: none;
  appearance: none;
}
form {
  padding: 0.75em 0.375em;
  outline: 1px solid red;
}
input[type=radio] {
  opacity: 0;
  position: absolute;
  width: 0;
  height: 0;
}
input[type=radio]:checked + .bubble:after {
  width: 100%;
}
button {
  background: var(--c);
  border-radius: 0.375em;
  color: #fff;
  cursor: pointer;
  display: block;
  margin: auto;
  padding: 0.75em 1em;
  width: 100%;
}
button:active {
  background: var(--c2);
}
/* Bubbles */
.bubble-group {
  font-size: 1.4em;
  display: grid;
  grid-template-columns: 1.75em 2.25em 2.25em 2.25em 2.25em 2.25em;
  align-items: center;
  margin: auto;
  width: 13.25em;
}
.bubble-group > strong {
  letter-spacing: 0.05em;
  line-height: 1;
  text-align: right;
}
.bubble-group:nth-of-type(even) {
  border-radius: 0.375em 0 0 0.375em;
  box-shadow: 2px 0 0 inset, 0 2px 0 inset, 0 -2px 0 inset;
}
.bubble-group:last-of-type {
  margin-bottom: 1.5em;
}
.bubble, .bubble-inner {
  display: inline-block;
}
.bubble {
  border-radius: 50%;
  box-shadow: 0 0 0 1px;
  cursor: pointer;
  font-size: 0.875em;
  line-height: 1.25;
  margin: 0.25em 0.5em;
  overflow: hidden;
  position: relative;
  text-align: center;
  height: 1.25em;
  width: 2.25em;
}
.bubble:after {
  background-color: #555;
  content: "";
  display: block;
  position: absolute;
  top: 0;
  left: 0;
  width: 0;
  height: 100%;
  transition: width 0.1s linear;
  z-index: 1;
}
.bubble-inner {
  background-color: #fff;
  font-weight: bold;
}

@media screen and (min-width: 361px) {
  button {
    width: auto;
  }
}
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