Slime games are popular again. Why? Probably because they are simple, they are grat, they are funny. As example see my review of this Slime volleyball game.
Slime volleyball game is simple 1 on 1 (can be also 2 on 2) game, with where simple object (sprites), like good old pacman game. Those simpe games were popular 20-30 years ago, but now again in past years we can see expansion on various slime sports 1-on-1 games, like slime volleyball or slime soccer, or even slime hockey.

Good sample of free slime volleyball game for 1 player is at MIT scratch:http://scratch.mit.edu/galleries/view/23004 (those are screen caps of Slime volleyball and whole other serie of slime games like: slime race, slime soccer, Slime tag, and similar, so You can just pick Slime volleyball and play)
My opinion is that Slime volleyball is excellent and better that any other volleyball that I ever playid because it is so simple and efficient that You can realy enjoj. I practice playing slime games and in past few weeks especialy Slime volleyball game on my work because i can easy close web browser when my boss came in, and because it is realy realixing to play with easy oblique characters, i realy love slime games!