Well realised, but very tedius.
This could have been a very good and incredibly well reaslised game with intresting features and a nice level of challenge, but it just became so tedius with levels in medium taking half a dozen attempts and the wining attemot taking more than 5 minutes.
Many levels, you ended up having to colect hundreds of green balls, where a single red ball could wipe more than 30 seconds worth of work. Infact, I see a previous review pointing out Med-4, which is when I quit as well. There, a bad luck spawn of few well spred reds was a death sentence, as you were losing 3 health, or so, a second and a singe red would wipe another 5 or so.
All in all, it felt like you were trying to pad the play time of the game by making levels needless long. No level in this kind of game should take more than a couple minutes for a successful run. It became very tiring and just wasn't any fun.