4P.de Forum

The story to this is pretty neat. For years I had suspected there was a bonus stage on level 4, because there was a piece of music in the soundtrack that was part of the Techno Party! suite, but wasn't ever played in game.

It seems I wasn't the only person who had been wondering about this. On 17th February 2008, John Girvin announced that he had located the entrance to the stage by examining the game's code (not the source, the actual compiled game code!). So for the first time in 16 years, the lost Speed of Light bonus stage was seen.

It's actually not that difficult to get into, but the entrance is somewhere that you would never fly into unless you were deliberately trying to die, so it's not surprising this has never been seen before. In fact, in my flythrough of level 4, the entrance doesn't even appear on the screenshots, because I had no idea there was anything of interest there.

The stage is in fact very similar to a bonus stage in one of the Project-X games. Presumably this is a coincidence. The bee begins moving slowly through a tunnel, and gradually picks up speed, while obstacles appear in its path. If you hit one, the bonus stage ends.
Quelle