Basically the classic Pac-Man game with new 3-D graphics. Eat all the pellets, dodge the ghosts, grab a Power Pellet to turn the tables and chase the ghosts for a while. The big new thing for Pac-Mania is the ability to jump, which can help you avoid the ghosts if you get cornered. Another slight difference is the scrolling screen; you can't see the whole game board at once, but it doesn't make much difference to gameplay.
The updated graphics make for an interesting change. The Genesis version of Pac-Mania is certainly a big improvement over the NES. The change in scenery helps keep the game fresh, so you don't feel like you're just staring at the same thing over and over forever.
The sound effects and music aren't bad either, but if you find them annoying you can turn off either or both in the options menu.
Pac-Mania is all about the points, just like the old Pac-Man game. Eat all the pellets to advance to the next level. The levels get progressively harder, and after you beat every board, they start over, with smarter and faster ghosts. Also in later levels, some of the ghosts can jump, too, so you can't always use your jump to get out of trouble.
In addition to the pellets, there are other items on the board to help you out or boost your score. Power Pellets allow you to eat the ghosts for a short time, Fruits give you points depending on which kind you pick up, and there are certain special items that may increase Pac-Man's speed, or act as a Power Pellet, etc.
The menu gives you a good amount of control for this game. There are four difficulty levels, and you can turn off the music or sound effects. Also you have Pac-Boost, which speeds Pac-Man up: you can turn it to always on, off, or set it to toggle using A or C button.