Going through Level class and closing functions when they look like they're ready. I think this is pretty good way to proceed especially when you get lost in the jungle of source code. The basic idea is find problems and try to find a solution for them even faster. When you program longer you start to understand what are the things that slow down development. I think there are only two things: 1) you did not find a solution for a problem and left the function/class unfinished and 2) bugs.
If it only were easy to fix all problems when you see them. But usually they are related to something else that needs to be done before you can continue. This is the difficulty in roguelike programming. With regular games you pretty much know what you need to add to make the game work like it should. With roguelikes you run into huge problems like artificial intelligence and the myriad of ways to interact with the game world. I hope my new style of programming brings some quick solutions.