Secret levels

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.

Publisher's Description
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.