Edit: Yay I scored a point. I think I figured out how the yellow dot works. You have some vertical rectangle as the input area and you just ran out of space to translate that to the angled field I guess?
The Yellow dot is the target that the ball will travel towards when it is hit. It slides along the floor of the court. The court is in 3D but the mouse is in 2D. So the translation means the mouse and target can not stay in sync. If you move the mouse left and right the target moves left and right on the court. If you move the mouse up and down the target moves up and down the court.
If someone has any suggestions on how this could be improved I would love to hear.
Thanks for the positive comments.
PS. I do not know if you noticed bu the game has some sound effects as well.