Come on in! Climb on the furniture! Try to get from place to place without falling into the "lava" (note: for once it's not real lava). If you happen to want to try things from the xkcd (http://xkcd.com/735/) comic, the Doctor will probably be very encouraging. Or you could boggle at the ridiculous exercise, but be prepared to be picked on if you don't play along!

Better hope you don't have any enemies in the class who will push you into the lava.