I found code in the api_demo for how to respond to mouse clicks and was trying to get something to happen on screen at the point of a click.
I just spent a couple days trying to figure out why my mouse clicks weren't doing anything. I finally figured out how to debug the actual x and y that I was getting with the clicks and the x was always greater than 1280. I had been using args.grid.origin_center!, so the x range should have been -640 to +640. After removing the origin_center! call and going back to default origin it works just fine. Is this a known issue with origin center?