.stopwatch {
  width: 300px;
  background-color: #0af;
  border-radius: 5px;
  box-shadow: 0 4px rgba(0, 0, 0, 0.75), 0 0 1px rgba(0, 0, 0, 0.15);
  padding: 15px;
}
.stopwatch, .stopwatch * {
  transition: all 0.15s ease-out;
}
.stopwatch .controls {
  display: flex;
}
.stopwatch .controls button {
  flex-grow: 1;
  margin: 0 5px 4px;
  padding: 5px 0;
  border-radius: 5px;
  box-shadow: 0 4px rgba(0, 0, 0, 0.75);
  border: 0;
  outline: 0;
  font-size: 16px;
  color: white;
  cursor: pointer;
  font-weight: bold;
}
.stopwatch .controls button:active {
  margin-bottom: 0;
  margin-top: 4px;
  box-shadow: none;
}
.stopwatch .controls .start {
  background-color: #5d5;
}
.stopwatch .controls .start:hover {
  background-color: #6e6;
}
.stopwatch .controls .stop {
  background-color: #d55;
}
.stopwatch .controls .stop:hover {
  background-color: #e66;
}
.stopwatch .controls .reset {
  background-color: #55d;
}
.stopwatch .controls .reset:hover {
  background-color: #66e;
}
.stopwatch .display {
  font-size: 50px;
  font-family: sans-serif;
  text-align: center;
  margin-top: 10px;
}
.stopwatch .display :not(:last-child):after {
  content: ':';
}