A number of secret levels are hidden in every world of Drilling Billy. These levels can be entered by walking off the screen in certain locations.
Some of the levels has [sic] entries into secret parts of the game. On these secret levels there is [sic] always power ups for Billy to play with. Unfortunatly [sic] it can be difficult to find them, but as a general rule I can tell you that the entries are always at one of the sides on the screen, so if you suddenly notice a monster that can walk beyond the borders of the screen or if a platform looks suspiciously placed, then take time to examine if Billy should be able to walk out of the screen here. Take for example level 7 in the Deep Jungle, here you can see a platform hanging out from the right with no apparent purpose, jump down to this platform and walk out of the screen. Voila, you are now on a secret level.