At first, it seemed like a sloppy mod rather than an expansion, but over time it grew on me as I noticed everything it had to offer. This is more of what the first game offered, but I have to say that the level design here is a lot more impressive, with tons of subtle details. The moving floors, the earthquakes, the objects that talk back, the way the ground has a more natural flow, such as the ice in the caves merging with the rock, all are good creative steps forward from the original and seem genuinely inspired.
My only complaint is that most of the time, it only uses assets from the original game. Same textures, same enemies, same classes, same items. It's still really fun, but I can't see why the only new things here are the levels. I would have loved to at least fight a new final boss, rather than an endurance run of monsters and all the classes. Oh well.