<div class="bulgy-radios" role="radiogroup" aria-labelledby="bulgy-radios-label">
  <h2 id="bulgy-radios-label">Select an option</h2>
  <label>
    <input type="radio" name="options" checked />
    <span class="radio"></span>
    <span class="label">First option</span>
  </label>
  <label>
    <input type="radio" name="options" />
    <span class="radio"></span>
    <span class="label">Second option</span>
  </label>
  <label>
    <input type="radio" name="options" />
    <span class="radio"></span>
    <span class="label">Third option</span>
  </label>
  <label>
    <input type="radio" name="options" />
    <span class="radio"></span>
    <span class="label">Fourth option</span>
  </label>
  <label>
    <input type="radio" name="options" />
    <span class="radio"></span>
    <span class="label">Last option</span>
  </label>
</div>

html { box-sizing: border-box; height: 100%; font-size: 10px; } *, *::before, *::after { box-sizing: inherit; }

body {
  display: flex; 
  align-items: center; 
  justify-content: center;
  min-height: 100vh;
  font-family: 'Lato', sans-serif;
  background: #2f2f2f;
}

h2 {
  font-size: 3rem;
  font-weight: bold;
  margin: 0 0 3rem;
}

.bulgy-radios {
  width: 38rem;
  background: #fff;
  padding: 3rem 0 3rem 5rem;
  border-radius: 1rem;
  
  label {
    display: block;
    position: relative;
    height: 1em;
    padding-left: 4rem;
    margin-bottom: 1.75rem;
    cursor: pointer;
    font-size: 2.5rem;
    user-select: none;
    color: #555;
    letter-spacing: 1px;
    &:hover input:not(:checked) ~ .radio {
      opacity: 0.8;
    }
  }
  .label {
    display: flex;
    align-items: center;
    padding-right: 3rem;
    span {
      line-height: 1em;
    }
  }
  input {
    position: absolute;
    cursor: pointer;
    height: 0;
    width: 0;
    left: -2000px;

    &:checked {
      ~ .radio {
        background-color: #0ac07d;
        transition: background .3s;
        &::after {
          opacity: 1;
        }
      }
      ~ .label {
        color: #0bae72;
        span {
          animation: bulge .5s forwards;
        }

        //adjust this if label is going to be more than 20 chars
        @for $i from 1 to 20 {
          span:nth-child(#{$i}) { animation-delay: $i * 0.025s; }
        }
      }
    }
  }
}
.radio {
  position: absolute;
  top: 0.2rem;
  left: 0;
  height: 2.5rem;
  width: 2.5rem;
  background: #c9ded6;
  border-radius: 50%;
  &::after {
    content: '';
    position: absolute;
    opacity: 0;
    top: .5rem;
    left: .5rem;
    width: 1.5rem;
    height: 1.5rem;
    border-radius: 50%;
    background: #fff;
  }
}
@keyframes bulge {
  50% {
    transform: rotate(4deg);
    font-size: 1.5em;
    font-weight: bold;
  }
  100% {
    transform: rotate(0);
    font-size: 1em;
    font-weight: bold;
  }
}

//This is sort of CSS-only; the JS below just sticks a span around each letter, so i can animate each independantly.
//(oh for an :nth-letter selector!)
const labels = document.querySelectorAll('.label');
labels.forEach(label => {
  const chars = label.textContent.split('');
  label.innerHTML = '';
  chars.forEach(char => {
    label.innerHTML += `<span>${char === ' ' ? '&nbsp' : char}</span>`;
  });
})