Through a friend’s blog, I found this wonderful flash game, which I’m totally addicted to.
Flash Element TD is a flash game inspired by the Warcraft III TD (Tower Defense). The aim of the game is to kill all monsters (bosses, goblins, birds etcetera) walking through a maze by shooting at them with war towers that you build on the grass around the maze. These towers costs gold, which is gained for every creature killed. Every eight level, one wood is received, which can be used for research. For another cost, the towers already built can be advanced at well. Through the game, as your towers and your skill advance, so do the enemy, becoming stronger and faster. My highscore is right now 786 points at level 23. Try beat that!
Update 2014-02-27, link fixed, thanks for pointing that out. (Btw, wow, seven year old blog post still being read?)