good job
i know how difficult it is to do collision control on an area larger than the stage (check out my racing game. same concept, somewhat smaller)... if you can work it out, however, you have an excellent game on your hands. good luck on future releases.
all i can say is that if you do collision control and touch up the game a bit (such as make the stage background green so it at least LOOKS like grass), you will definately be on my favorites list.