In Trajectory your main goal is to shoot balls with the right angle and power, if you want to hit the green orb and continue to the next levels. It takes some real skill to make your way through all 50 levels. Of course there are some obstacles to overcome and you may need more than one attempt to pass some of its levels. But isn't this the main reason we like those games? It's really worth playing till the end. And every level you beat is a little personal achievement!