You can certainly, as slashdotters assuredly will, endlessly debate copyright law and trademarks and the DMCA and how close to using someone else's ideas you can get before triggering legal action, but I maintain that the simplest method of completely avoiding the issue is to make a game that isn't anything like what someone else has already done. Instead of trying to just barely skirt the law, make your mark as an originalist, as a creator. It's /much/ more difficult to do - you might even respect copyrights and trademarks a little more afterward, although you also may not - but it's still much easier than lawyers' fees and court dates and trying to squeak your imitations past the DMCA. You'll also almost certainly find that it's much more deeply satisfying to create something entirely new, entirely your own, than to clone someone else's work.

Making a Pac-Man clone should be a requirement for anyone learning about game coding, there's no doubt, but you don't /distribute/ it. If Namco Bandai wants to put Pac-Man on the Android Market, that's their decision: you should come up with your own thing, and put /that/ on the Android Market. Besides, does the world /really/ need another Pac-Man clone?

This is a scientific restatement of Pascal's Wager, and the same logic can be applied to any action: if the chances of me blowing up the universe by turning on my blender are not provably zero, I shouldn't use the blender, because the risks [destruction of everything] are so high. It's mathematically and logically sound, but ultimately immaterial: at some point, one has to weigh the evidence with which one is presented against the degree of certainty with which we can determine the risk. Or stop using the blender altogether, and then it's no more frozen daiquiris for any of us.

Seconded. [It's called "Hyperspace," in the US, "Space" in the UK, as I recall.] My daughter and I watch it about once a year, as a reminder of those pesky origin questions.

Also incredibly powerful as a teaching tool is Cosmic Voyage, which teaches cosmology and /scale./

Last year, I did a demonstration for my daughter's class where we all went outside and built a scale model of the solar system. Even moreso than video presentations, this kind of "hands on and moving around" education keep the attention of children of all ages, and, even if they are incapable of fully grasping its ramifications /today,/ I assure you they don't forget such experiences, which serve them well as they age and learn.