Hands-down the GOAT when it comes to mod maps. I went through 3 devices (phone, tablet, new phone) before I was able to run this level without massive framerate drops, but the fact that I kept trying should tell you everything. This level is absolutely ENORMOUS, with multiple viable paths (some taking such different routes that you can complete the level multiple times without crossing the same ground twice). It's admittedly pretty easy to get turned around your first couple of trips through, but given that so many SRB2 maps are short enough to be beaten in under a minute it's a testament to this map's sheer breadth that you have to navigate it by landmarks rather than simply holding forward. If you've beaten the main game and are looking for something with as much polish as a vanilla single player campaign level this should be your very first stop.