You start off on the easy level (although there is a practice "Zen" mode with no opponent) and the first person to win 5 points wins a game and when you win, I believe is 5 games, you move on to the next difficulty level. Certainly, as you progress the AI opponent seems to get faster and the ball comes back to you quicker. I found the only way to get points as the difficulty increased was to hit the ball on the edges of the opposite wall and this is called a "rim" shot and gives you 200 points. You also get 200 points for doing an "ace" and extra bonus points if you beat the AI 5-0 etc.
The play area seems a bit "cramped' to me. Not so much width wise but front to back. The ball spawns on a pedestal in front of you and if you are standing too far forward you can inadvertantly knock it off and get a -100 point reduction for a dead ball as it doesn't rech the front wall.
It would be nice if it included a coop option to increase replayability. The graphics are nothing special but get the job done and the audio is quite good with futuristic music and the robotic voice of the AI opponent.
The game does get your pulse running though. After 30 minutes my heart rate averaged 130 bpm, I did 2604 steps and burnt 322 calories. Not bad !