body {
  font-family: sans-serif;
  background-color: #23b2f9;
  background-color: hsl(240, 44%, 55%);
  color: #fff;
  width: 100vw;
  height: 100vh;
  display: flex;
  margin: 0;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.container.fullsize {
  width: 100%;
  height: 100%;
}

* {
  box-sizing: border-box;
  padding: 0;
}

.centered {
  position: relative;
  width: 80%;
  max-width: 400px;
  display: flex;
  flex-direction: column;
}

h2 {
  margin-bottom: 0;
}

.score {
  position: absolute;
  right: 0;
}

ul {
  padding: 0;
}

button {
  margin-top: 2em;
}

button, .button {
  position: relative;
  text-align: center;
  cursor: pointer;
  border: 2px solid #fff;
  background: rgba(255, 255, 255, 0);
  color: #fff;
  font-size: 1.5em;
  line-height: 2em;
  margin-bottom: 1em;
  animation-duration: 1s;
  transition : border 500ms ease-out;
  transition: background-color 500ms ease-in;
}

button:hover, button:focus, .button:hover, .button:focus {
  background-color: rgba(255, 255, 255, 0.2);
}

.button .countdown {
  position: absolute;
  height: 100%;
  top: 0;
  background: #0586c7;
  background-color: hsl(240, 54%, 25%);
  animation-duration: 3s;
  animation-name: countdown;
}

@keyframes countdown {
  100% {
    width: 0%;
  }
  0% {
    width: 100%;
  }
}

.button .center {
  position: absolute;
  top: 0;
  width: 100%;
}