'Neato. I'm pretty computer/internet disabled myself. I usually let my DH handle all of the purchases on the web. My one foray into purchasing on-line by myself was for the Standard Deviants' tapes, which I still have not received!
So I am not the best one to ask. I can ask DH (who is currently not answering his phone at work.)
It looks like you can get Physicus from an Amazon seller for under $4 buck though, not including shipping. A free download would be great, but it might just be a teaser. (i.e. it may just let you see the first beginning screens, in order to get you hooked.) But the games are fairly old by now, so they should be cheap. And they come in Mac versions, too.
We also have a cool game called Crazy Machines that DS really liked. It has over two hundred puzzles that are based on pulleys, gears, etc. You start out with a target (say a ball) and try to put the necessary gears, power sources, or dynamite in order to get the target to the finish line. Very Rube Goldberg-like!
http://www.gamespot.com/pc/puzzle/crazymachinesthewackycontraptionsgame/review.html?om_act=convert&om_clk=gssummary&tag=summary;read-review
There are dozens of different pieces, all having unique properties. The game includes various types of power sources, balls, wires, balloons, gears, conveyor belts, boxes, catapults, pipes, widgets, and other knickknacks that you'd expect to find in a crazy inventor's lab. You'll even find unusual items like steam pistons, working blimps, cannons, dynamite, and robots, all of which help to make complicated work out of simple tasks. What's most impressive, though, is how the game seems to incorporate logical physics into its experimental setups. Allow a balloon to drift too close to an open flame, and it will pop. Heat up a boiler, and it will provide power to turn a steam piston. Different types of balls will have different properties that reflect their weight and elasticity--tennis balls, for example, bounce high but don't have the same force in a collision as billiard balls. The point is that the game allows you to use common sense as you try to solve the puzzles it throws at you.
