good (100th review!)
I think it's a good game, with good diffuculty, and plenty of fun. The diffuculty comes mainly from the start when you have hardly any cash, and then have to build up your air defenses, and then you let ground penguins through, etc... but once you get yourself some cash, it's easy, especially with the missile towers. A good trick is to make a short line (depending on how much space you've got) of the lowest towers, just infront of the entrances (heading away from the entrance). Upgrade them to full, and then get a flack tower on the end, and upgrade that to full. That should be enough to hold off all air units for ages, while you work on your ground defense. When you are ready, put a couple of missile towers on the end of the lines, and upgrade to full. This should be enough. Now build a maze on your ground defense out of missile towers. This should be enough to win you the game.