implementing "run"

We're going to need a global to control the game.

var g_running=false;

The stop function will simply be:

function stop() {
  g_running=false;
}

The run function is not quite as simple:

function run() {
  g_running=true;
  cont();
}
function cont() {
  if (g_running) {
    one_step();
    setTimeout(cont,150);
  }
}
Improving the layout
#game {
  margin-top:3vmin;
  justify-content: center;
}
#pane1 {
  margin:1vmin;
  padding:.5vmin;
  border:3px solid brown;
}