Made it to 100. At a certain point you realize your going to lose because you ran out of space to move meaningfully. Also the art style is very smooth and dull.
For longer playtime I suggest a wider board.
You could also segment the game in stages, adding colors to the generator each level. (Red, then on LV. 2 it's Red+Blue, Lv3 R+B+G. Etc.)
If you have the coding skills I suggest adding in power ups. Not like the ones in the candy crush type games, more like the system in Bloon Monkey.
Over all 2.5, look forward to an update.