Perplex Puzzle looks nice, however I just can give opinions/sugestions on City Edge as it's the only level that I have played...
I like the engine and the level design, it has lots of interesting areas but I guess that some new gimmicks would make the level a lot more interesting...
Maybe when you go to past you could just go a little bit to the past, like instead of a city become a forest with lava, it could become an old city, with old architeture and some buildings being constructed in the background, so it resemble more like a city in the past, not like anything in the past...
One of my favorite things on Sonic CD was that when I was in another time zone I had the same level music remixed and I miss it here, because the music is aways the same. But I guess it's hard as you are using music that already exists but maybe it would be better the music were changed in different time zones.
Other than that I like your game, are there chances that this will be one of the finished games on sage?