Pretty good, just a few things.
There are some issues.
Because the gem you create is always a random color, it makes it difficult to form an actual strategy , relying more on luck to get better gems. Even if only from a concrete set for each level, you should be allowed to choose the color of gem you make. The same thing happens with gem fusion. If you have more than two of the same type and decide to fuse, the game will pick which gems to fuse at random. This makes it almost impossible to fuse the gems in the way you want if you have a large stockpile of the same type, such as one made up of level one gems for the sake of bombing runs.
Because the different modes are dependent on level rather than progress, it does require the player to grind the same few battles repeatedly, which can get old. It would probably be better and makes more sense to unlock the different modes in levels by beating the earlier modes, i.e.; The player beats normal mode, then unlocks survival, or some similar progression. This cuts down on the grind, but still allows for the revisiting of stages for level building. It will also make level building more entertaining since the player will never be required to do the same stage in the same way.
For some reason, using the shift macro for gem bombs didn't work for me. I haven't tried on a different computer, so it may just be something wrong with that, though I would check anyway.
Beyond that, it's a pretty solid game. I did like the use of both traps to put on the travel field and towers to put on the side. It adds an extra level of strategy that some tower games lack. I played it through pretty far. Only my lack of tolerance for grind kept me from going much further. If you can cut down on that, it'll all be good.
