Like advengine-tdd, a rewrite using test-driven development. Includes levels from similar oldschool games Rescue Rover, Chip's Challenge and Sokoban. Obviously I could do this much more quickly with a higher-level game engine like Unity, but at the time I hadn't used any such thing. The fun here was in writing my own engine.
Future plans: It would be fun to flesh this out with more levels and features, if I think of an interesting new spin to put on the old games it's based on.