What is the name of the online defense-type game where you would have to fend off a wave of blue that would spawn from nodes and based on how many layers deep the wave of blue was it got darker

More info: You could build various towers in this game, and it was on addictinggames a long time ago as a trial version; however, you could buy the full version online on the games website. Also, the goal of the game was to fend off the blue that was being pulsated by these nodes. You would have to build up your towers further and further to the nodes until eventually you neutralized the blue they spawned. The game also had a grid-like structure to it. There were many levels you could play on and the level selecter screen looked kind of like a big spiral of planets, each one being a different level. Does anyone have any idea what I am talking about?