It really seems like an in-game level editor where I can doodle out levels and test them right away is a big deal when it comes to just being creative and trying things design-wise. Granted, the wait time between builds would be smaller if I would, you know, use makefiles.
Nova the Squirrel's level design process was very different. With the bigger and much more complex levels I spent a lot more time both editing and testing levels, running through the path I'd made multiple times, trying different things and just generally getting lost in my own creation. There were actually a lot of points where I'd feel like running through a bunch of levels just for fun rather than particularly to test anything.
