body {
  background-color: #fafafa;
  font-family: -apple-system-font,"Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "WenQuanYi Micro Hei", sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-font-smoothing: antialiased;
}

.container {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  margin: auto;
  width: 800px;
  height: 600px;
  border: 1px solid #e6e6e6;
  border-radius: 5px;
  box-shadow: 0px 1px 4px 0px rgba(0, 0, 0, .2);
  text-align: center;
  background-color: #fff;
}

header {
  margin: 2rem auto;
  color: #333;
}

footer {
  margin: 1rem auto;
  color: #999;
  font-size: .8rem;
  font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace;;
}

footer a {
  color: #999;
  text-decoration: none;
}

section {
  position: relative;
}

.panel {
  position: absolute;
  left: 50px;
  box-sizing: border-box;
  width: 300px;
  height: 400px;
  border: 5px solid #00c086;
  border-right: none;
}

.btn-play {
  margin: 5rem auto;
  display: block;
  width: 8rem;
  height: 3rem;
  border: 1px solid #00c086;
  border-radius: 1.5rem;
  color: #00c086;
  font-size: 1.5rem;
  line-height: 3rem;
  text-decoration: none;
}

.score {
  margin: 1rem auto;
  color: #333;
  font-size: 3rem;
  font-weight: bold;
}

.score-label {
  margin: 0 auto;
  padding-top: 1rem;
  width: 100px;
  border-top: 1px solid #999;
  color: #999;
  font-size: 1.5rem;
}

.playground {
  margin-left: 300px;
  background-color: #00c086;
}