Very nice game, but a little basic. Some enemies seem to behave differently (vulnerable to different weapons), although there is no indication with color or shape. A minor bug: Once you click on a unit to build, you can't change your mind and "unselect" it anymore, forcing you to build that even though clicking it could have been a mistake.<p>Also it's a bit annoying that if you want to build the same unit type multiple times, you have to click on it every time again. Keyboard shortcuts 1-4 to select each unit to build would be great. Another shortcut for upgrading and selling, and the game would be a lot more usable and fun to play.<p>Still, quite addicting game! :-)