Love the game. Interesting content, interesting gameplay, and interesting concept. Ignore Kwing (who rants about the gameplay being slow, the hints being unhelpful, and the environment not being immersive). He lives in a world where every hurdle in a game must be explicitly spelled out or he cannot solve the puzzle. Its a disease of modern gaming that I am thankful this game avoids. It could also be that he simply isnt smart enough to solve simple puzzles but there is no way to tell.
The gameplay was simple with a well thought out mechanic. Better to focus on one thing and do it well than to focus on more things and do them poorly. The art was pleasing and the music helped to set the mood of the game. The puzzles were logical and the hints were unobtrusive. At times, I thought the hints (not the control hints but the logical hints) gave away a little too much but all and all great pacing.
The concept of allowing time to pass to solve obstacles has great potential. I like what you did here but I think its applications could go wider. Cant wait to see what you turn out next.
Above all else, don't sacrifice the gameplay or the artistic direction of the game for the modern era COD/GTA/MADDEN/AC crowd. Games like 400 years are where the industry needs to go.