I dunno... If you swap the lawn or clay surface to something much colder and smoother.... This game reminds me of another... Can't quite put my finger on it... lol
The fill circle function is quite fast. Two paddles and a fast moving ball... Have you tested the number of circles before lagging occurs? Homework...
I like the "Help Me" option... Unlike most 'tennis' games, I could actually hit the ball more than once... nice feature.
In regards to graphics, would I be correct in assuming that, curved paddles would be preferred so as to maintain an air of unpredictability?
Originally, you had the player setup as a rectangle... But, calculating the distance between two circles, would be quicker than including collision detection... Cool...
If ever you decided to use collision detection, you could use AABB, because the ball is quite small and can be treated as a square... On the subject of the ball... The colour could be white, yellow or even lime green. Steer clear or black. Black would make it look like a puck. Puck? Interesting... Just a thought...
Speaking of lawn and clay... perhaps either allowing the player to choose or randomly select a surface could effect the player's "friction". eg: if the surface is clay, then the surface friction is less - similar to ice but not so much - ice? Interesting.... and the lawn would have greater friction so as to make player movement more responsive... Just another though...
Here's another weird thought... I know... three in one day... Who knew? lol If the player is using the 'easier' paddles then perhaps the player's paddle can reduce in size with each ball strike... Striker? Interesting... Just yet another thought... I'm going to stop there. Fear of wearing out the old grey matter is reason enough... But, the best reason is, coffee...
Have a great day!
J