A game like Pong could translate to a tennis game quite well - with a bit of tweaking, using Graeme2408's suggestions here's a thrown together concept
Just something else you might want to consider when creating the skewed view is scaling. The top edge of the court (where the opponent facing you stands) is slightly narrower than the bottom (nearest) edge, e.g. 80% of the bottom edge. As the ball travels up (into) the screen it should gradually get smaller until it is the same scale as the top edge when it arrives there, i.e 80% of it's original size. By then it should also be moving 80% of it's original speed, otherwise the ball would appear to be speeding up as it reaches the far end of the court. The opponent at the far end of the court should also be scaled, so in this case 80% of the size of the player nearest to you, and move 80% of their original speed (since the court is 80% smaller at the top edge).
Hope I've explained this ok.
I think the easiest way to pull this off is the shader for skewed view as someone mentioned above. You might not be able to port it to other runtimes but if that's not an issue it would make things significantly easier. The mode7 object might be too skewed of a view, but maybe you can adjust that in the extension's settings, dunno I've never really used it. You'd also still have the portability issues with mode7 as well.
Thanks for the positivity hoyoyo80, I played with the above example and have created a pretty good tennis engine based of Pong. I'll post a clip here soon. Can anyone provide a basic example of how to use the perspective object to make the screen wider at the bottom and not so wide at the top?
I tried yet it only effected the top part of the screen.
Worked it out, The perspective object works nicely, yet it resizes what it overlays. Therefore the size of what you want to change the perspective of needs to be taken into account. I was getting a black area, or it would only change the perspective for the top part, turns out it's because the skewed image will take up a different size on screen. It's a lot of mucking around for an effect that doesn't change the game play, I'm not certain I'll bother?
Here's a video example of my progress. On the left is the game detectors and engine; and on the right is the game. Still a work in progress yet it works quite well so far.
it would be nice if you had even a few frames of shadow size changing to sell the visual of the ball bouncing. Also, ball size could change if there is an obvious lob. But it is looking pretty awesome overall. Can't wait to see how you add the perspective skew.