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.