To obtain the Copper Key, what challenge must Parzival complete?

Before Wade can acquire the copper key, he must win a video game Joust against Acererak. He loses the first game, but successfully wins the last. When it is over, Acererak morphs into Halliday's avatar, Anorak, and he gives Wade's avatar the copper key. The key contains written a clue to the location of the gate, which Wade figures out immediately.