I reaaally like the idea of the mode switch being between day and night, which changes certain details of the map.
The controls unfortunately sucked the fun out of the game for me, there is a large amount of smoothing on the mouse and character movement in general, which made me feel like I was underwater at all points of the game.
With a few things tweaked, and some additional feedback given to the day/night switch like sounds and a smoother transition, it would be a really great experience.