Yeah, I can defeat it. It doesn't defend long shots very well. It's also generally better to try to return its shots immediately instead of juggling, so it can't position well for the return. If the opponent is close to the net then you can try hitting the ball up for it to quickly bounce back down behind him. You can also try kill shots near the net, but those can be risky.

Yeah, I spent too much time this morning mastering this (thanks for sharing!). For me the key was realizing that - unlike most modern platformer controls - jump height isn't affected by the length of the key press. So you can quick tap jump, then use the direction keys to aim your spikes. The ground-dive is also quite useful.

Once you grasp these controls, you stand a chance. Once you master them, the AI becomes trivial to beat by this method: When serving, jump and perform a horizontal spike at the apex. The AI will defend it, then reliably do his own horizontal spike from the backcourt. Meet it at the net and spike it diagonally downwards. Works every time! And now I can rest (work).

I could only win because I found a trick to score when AI serves, jumping backwards one second after AI jumps returning long, but timing must be exact, also if you stay in the middle 90% of their shots are towards the back very predictable and lastly is about the timing every time the opponent returns the ball it jumps so when you see a jump you can meet the ball in the air for a quick return.

Yes, there is a trick. If I recall correctly... You can get all the way back, and hit the ball from there.

I can score every time it serves by jumping in the back row and power hitting the ball to the far side. That keeps it from scoring 2 points in a row which makes the game quit winnable.