.flex {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-start;
  justify-content: space-around;
}

.mdl-card {
  margin: 0.5em;
}

.key {
  width: 100%;
  height: 6em;
}

.center {
  text-align: center;
}

.wide {
  width: 100%;
}

code {
  background-color: #333;
  color: #fff;
  padding: 0.1em;
}

img {
  max-width: 20em;
}