The game is a little difficult to pickup at first, and I stress that a lot because this is a game where a tutorial is heavily needed, but once you do its quite enjoyable. I wish there was different method for placing tracks, like laying them out in a line or placing them with the left mouse button and selecting the direction with a number pad. Music would be nice.
Also, if you wanted to take this to the next level, you might do well to consider dynamic design, like add little enemies that place blockades or steel your green balls but won't go near the red ones so you have to construct the belts in a knowledgeable way. Add a 3 star scoring system for different stages and you have a game my friend!