Retrobooster now has a full complement of levels, enemies, and weapons. I have moved on to testing and refinement. One of the big unsolved challenges remaining is how to attract co-op testers. There are many testers currently hammering away at almost every aspect of the game. However, the only feedback coming in so far is for single player mode.
Throughout development I have spent some time playing multiplayer games with in-house testers. I'm generally too good at my own game, so I would take a disadvantage by playing with a game controller (I have much more practice with the keyboard and mouse). Unfortunately, this is only a half-measure. When it comes to proper testing you really need to take the developer out of the mix, but it has been very difficult to get multiple testers together at the same time. Like every other problem faced during development, this one is also solvable. I'll keep at it and find the right solution one of these days.
The plan was to release Retrobooster in 2013, but that goal is looking more unrealistic all the time. It is due to many factors, not the least of which are new-found testing difficulties. The good news is that the end of development is definitely in sight. Hitting the recent milestone of beginning full game testing was incredibly satisfying. There's no stopping Retrobooster now. If this article has piqued your interest, go try the free demo and lend me your support on Steam Greenlight.