Mario Maker: Create Your Own Super Mario Levels
So much potential in this - a few years ago myself and a bunch of friends were obsessed with ROM hacks for Super Mario World for the SNES; some of them were just really well-designed levels, and some of them were absolute hell, basically requiring the use of an emulator to save states and rewind. It created a completely different feel of game, and the simple and consistent physics of a Mario game was the perfect limitation for weird and strange things to happen.Here's a video of one of one of the difficult levels: https://www.youtube.com/watch?v=teAqRZX4hbY