The general thrust has been to get the level reactor implemented -- this is of course the standard video game gimmick where you have to seek out the reactor and destroy it, causing the stage to self-destruct. While you're attacking it, the reactor will throw off sparks which veer randomly about and damage anything they hit, including you or other enemies that are in the vicinity; I decided to start by getting the sparks fully implemented, adding enough options to the XML setup files so that they could be created just like any other enemy.
This took a little while. Among other things, it turned out there are lots of fiddly little details to this -- for example, sparks should be able to pass through each other -- which ended up requiring a full rework of the collision filtering system. But that being said, the collision filtering system needed to be reworked anyway, and now it's much more flexible, allowing me to set what every specific enemy or object collides with instead of being limited to a few collision filter groups.
So far so good, then. A lot of the graphical effects are only half-done, though, and there still isn't a proper damage system for the player ship. I'll have to either implement that next, or else skip over to the reactor proper.