app.css

body {
  font-family: 'HelveticaNeue-UltraLight',
               'Helvetica Neue UltraLight', 
               'Helvetica Neue', 
                Helvetica, 
                Arial, 
                sans-serif;
  margin: 0;
  background-color: #efeff5;
}

.stopwatch {text-align: center }

.stopwatch-timer {
  font-size: 76px;
  font-weight: 100;
  line-height: 160px;
  margin: 0;
  border: solid #c3cfd0;
  border-width: 1px 0;
  background-color: white;
}


.stopwatch-laps {
  padding: 0 0 0 20px;
  list-style-type: none;
}

.stopwatch-lap{
  font-size: 20px;
  line-height: 60px;
  padding-right: 20px;
  text-align: right;
  border-bottom: 1px solid #d9dae0;
}

.stopwatch-lap strong {
  float: left;
  color: #7f8083;
  font-weight: 100;
}

.stopwatch-lap strong::before {content: 'Lap '}

.btn {
  font-family: inherit;
  font-size: 20px;
  display: inline-block;
  width: 72px;
  height:72px;
  margin:24px;
  padding: 0;
  cursor: pointer;
  letter-spacing: 1px;
  border: 0;
  border-radius:50%;
  outline: none;
  background: white;
}

.start-btn {color: #4bd761}
.stop-btn {color: #fd3d2a}