body {
  display: flex;
  flex-direction: column;
  height: 100vh;
  width: 100vw;
  margin: 0;

  font-family: Arial, Helvetica, sans-serif;
}

h1 {
  margin: 1em 1em 0;
}

#arena {
  flex: 1;
  margin: 1.5em;
  border-radius: 1em;
  border: 0;
  background-color: lightgray;
  position: relative;
  overflow: hidden;
}

#arena .pointer {
  width: 2em;
  height: 2em;
  border-radius: 1em;
  position: absolute;
  margin-left: -1em;
  margin-top: -1em;
}

#messages {
  height: 10vh;
  overflow-y: scroll;
  margin: 0;
  padding: 0;
  list-style: none;
  border-top: solid 1px slategray;
}

#messages li {
  font-family: 'Courier New', Courier, monospace;
  font-size: .7em;
  border-bottom: solid 1px gray;
}