I really liked Dark Aether. With a change of environment it changed the game plan, creating a monstrous and brutally hostile world, a step up from a simple change in scenery as seen in most other games that use the light/dark theme. It thus turned much of the game into a series of fiendish map and logic puzzles, as well as throwing increasingly hostile gribbilies that seem utterly alien even compared to what was already on Aether itself.