Billiards
A ball is launched from the bottom left corner of a rectangular billiards table, at 45 degrees to the sides. If it continues to travel - bouncing off the sides of the table - will it enter a pocket (at a corner of the table)? If so, which pocket?
Once you have a prediction, press "play/pause" in the app to launch the ball.
Then drag the grey dots at the bottom right/top left of the table to change the dimensions of the table.
What other questions could you ask?
(Only after you have investigated: you can click the checkbox towards the bottom left of the app for insight into one way of thinking about the problem.)