You basically have to just eat all the dots in the level and avoid the ghost things. Once you do that, you go to the next level.
If you get the glowing orb, you are able to eat the ghosts for more points or to save you if you get stuck (it only lasts for a few seconds though). If you eat two or more ghosts in a row you get double the points.
You can also get the fruit that appear sometimes under the ghost cage thing for more points.
That is really awesome! And you know, they say that video games affect kids, but if that were true, we'd have a whole generation running around in darkened rooms, listening to repetitive electronic music and taking magic pills.