iOSのボタンをCSSでまねる

まねてみました。

DEMO

See the Pen Button by kimmy (@kimmy) on CodePen.

SCSS

body {
  background: #1e1e1e;
}

.btn {
  box-sizing: border-box;
  position: absolute;
  top: 0; bottom: 0;
  left: 0; right: 0;
  margin: auto;
  padding-top: 8px;
  border: solid 1px rgba(255, 255, 255, .5);
  border-radius: 50%;
  width: 73px; height: 73px;
  color: #fff;
  font: 34px HelveticaNeue-UltraLight, "Hiragino Kaku Gothic Pro", "ヒラギノ角ゴ Pro W3", Meiryo, "メイリオ", sans-serif;
  text-align: center;
  background: rgba(255, 255, 255, 0);
  transition: background .4s ease-in-out;

  &:after {
    display: block;
    position: relative;
    top: -3px; left: 2px;
    font-size: 10px;
    content: "JKL";
    letter-spacing: .3em;
  }
  
  &.on {
    background: rgba(255, 255, 255, .5);
    transition: background .1s ease-in-out;
  }
}