Minor status update:
The RL issues that were stressing me out have been assuaged- at least for the time being. As such the game is no longer on hiatus (although technically it hasn't really been on hiatus since I went and finished those previous two levels).
I'm currently making good progress on Chain Man's stage- I've finished planning the layout and am in the process of adding tiles and collision to it.
Past that, I plan on adding a couple mid-game cutscenes, putting in the options menu, and finally adding in the save system before moving on to the fortress stages.
I'm hoping the fortress stages don't take me as long to develop as the RM stages have- while they do generally reuse a lot of content from the robot master levels, they will have some of their own unique enemies and gimmicks, particularly the earlier stages.
In any case, though, the game is getting close to being officially 50% complete.