Fun defense game with a wide variety of units and enemies! The random draw of upgrade is a nice touch. But I'm not so sure the upgraded units are worth their price.
Will you continue to update your 1 Million Sprites pack? Or have you decided to keep all the new ones exclusive to this game? (not that I will use them in the near future, since tou've already gone way further than me in the direction that I had in mind)
Good job anyway!