Nice little game. Too bad it's so short - i've finished in on all 3 difficulties and got all the achievements in under 3 hours. It could be a good thing, though, because people can get bored pretty easily after all.
Like Argenteus said... more movies or new enemys would be good or even more levels. but still a very good game =)
I like the idea behind this, reminds me of a tower defense game I used to play competitively.
Some of the special challenges don't work
Its not the most original game, but it is entertaining to play for a good hour or two.
There seems to be an amount of randomness in the crystal strategy, i could do the same thing and they would react differently, also they always engage the closest plant no matter what and dont tend to rely on regeneration even when they have it. some levels are really fun while others just take a few decoys and well placed meteors. the game could be made longer if you added challenges for triple star difficulty, maybe make the requirements of completion add ons to the original challenges, but more or less for fun (like people who beat the game and are bored)