Slipinator's the level editor, in case you were wondering. And it's starting to take shape! almost three hundred lines in, and we have a functional level canvas class that lets you place blocks on the level (with a grid to make it easier), and also drag and drop other objects onto. At the moment only the block editing is implemented, but it works perfectly! Here's a screengrab:
Click it to view full-size as per usual. At this point, clicking in a square will add a block there and clicking on an existing block will remove it (the latter of which took a very long time to get working). The graphics are still placeholders at the moment, as is currently the case for nearly everything in the game. But graphics will come as soon as level development properly begins.
Anyway, back one the subject of the level editor, the saving system is also working. It can properly create a level folder with the *.slf file inside, and append the name of the folder to a list of custom levels which is read by the game. Editing level properties isn't yet in, though, as we've not finished deciding on those. The basic idea is that there will be a level name and difficulty rating for each one (supplied by the user), and possibly an author. But that'll all come after the main challenge - implementing drag-and-drop!