Not bad, understanding required
This isnt as bad as people are making out, yes the graphics are poor. But this is a fun game with kids in mind.
As regards to the tennis, this will work if you stand around 8 feet or more away from the sensor, although I havent got that sort of room in my house. The tennis revolves on timing - if you are too early with your move it wont work, if you are too late with the move it too wont work.
Buy this game if you have room - tennis is quite good with space in your house