Good and bad things
There are some good and bad things I experience in this game.
The good:
-The 13x13 labyrinth idea is quite nice!
-I love the walls and mazes you can build, and the boost towers. The building of mazes isn't new of course (see Desktop Tower Defense), but in this game it's interesting because it adds yet another strategy to the already so many strategies. In the first game there were only gem towers, the second added traps, now the walls, and the boost towers were added. Yay :)
-The story is interesting. I also like those demon effects in the epic levels!
-The bad:
-The upgrades are quite bland imho. I found the upgrades in the first game the most interesting, in the second game they were already somewhat less interesting, now even less. You start with only two possible upgrades and then unlock more, and almost every single of the upgrades is to make a certain gem type better. The thing that makes the upgrades bland imho, is that they don't provide a lot of strategy. If there are a few more expensive but more "special" upgrades (special as in, do something more original than just make some gem type better of give more mana), it adds more strategy by letting you decide which one to take for this map. Basically, to me having more different types of upgrades with less possible levels for each, is more fun than having fewer types of upgrades which can each to up to 30 or even infinite levels.
-The fact that monster color order was always the same. I'm not sure if gems of opposite colors are more effective against monsters of the opposite color (I think in earlier versions it was), but if the monsters are going to start at green and end at red in every single level, it's kind of the same color strategy for every level... I kind of ignored this while playing though and just built my favorite gem type the most (the red ones), hoping they wouldn't be getting less effective against the red monsters appearing later.
-Is any of these challenges obtainable at all in the non paying version? I mean, 100 waves if you can unlock only 15 extra?
The Ugly:
-I have nothing against monetization of a game. However my least favorite type of monetization (below ads) is to have it so that a non paying user is greminded that there exists a paying version for the duration of the whole complete game. So this was a downer for me, I don't visit Newgrounds for this.
-The GamerSafe button in the bottom left is a real nuisance that is very annoying and in the way. It makes an annoying popup appear over the glass ball that reveals levels with challenges.