This hack had a really cool start, but the last two levels put it over the edge. The gimmick in the castle was cool, but the level design definitely didn't match that. The last level felt annoying to play after struggling so hard on the castle.
The first few levels are decent, but the difficulty ramps up in a pretty unfair way and the gimmicks aren't really well-executed.
There should probably be an auto-save feature, though that won't save you from the last few levels sadistic designs (especially the final level).
A lot of cramped corridors and well-placed enemies will often be the cause of death in some of the more frustrating levels. The fish spam in the ice level was a treat. Some pretty good ideas/level themes, but the unfair difficulty really throws it off.