Complete Adventure on difficulty 1 or higher.
Complete Adventure on difficulty 2 or higher.
Complete Adventure on difficulty 3.
Catch the bat.
Find the secret Warren Robinett room.
Find and pick up a bridge.
Find and pick up a magnet.
Slay the Yellow Dragon, Yorgle.
Slay the Green Dragon, Grundle.
Slay the Red Dragon, Rhindle.
Have the bat kill one of the dragons for you.
Touch the difficulty selection number with your square.