This is a new Bloons game. As well as in the other ones, you are monkey that pops balloons throwing darts. You define the angle and the power of the throw with your mouse and need to pop the required percentage of the balloons in the level. Apart from new levels, this game has some new level elements and features.
Other Bloons Games at Sugar-Free-Games.com:
Bloons Tower Defense
Bloons Tower Defense 2