+Tom Scott -- If you want to see a game that takes all of this into account, play Portal, by Valve. You will love the science (and it is LOADS of fun!)<br><br>I don't suggest you look it up on the Internet, though. You will get a lot of spoilers that will really ruin the experience for you. Happy gaming!,(reply>), Revi M Fadli they do, in the neurotoxine "factory" you create portals on moving walls,(reply>), Jared Focose he has already played it,(reply>), Plus- take a belt, then two portals above each other. Feed the belt through one of the portals, then click it to its own buckle. Will it "fall" or stay stationary? Also, would you get a one-sided vertical treadmill? What if you increased the distance between portals? Would there now be two buckles seen between portals? What about decreasing the distance? the possibilities are many,(reply>), @Adam Mullarkey From what I've read, portals never move relative to each other in-game(<b>spoiler alert</b> save for parts too dramatic for anyone to notice it <b>spoiler end</b>). What would happen if one portal is stationary, and the other one is put on a quick moving platform that moves perpendicularly to its plane, so that it moves towards a cube and gulps it? Would the cube fly out of the other portal, or would it just plop out with almost no kinetic energy? Some people argue that it's the latter, the reason being that portals conserve energy and momentum. But considering that portals can move things that enter the lower one without slowing it down on exit(and vice versa), they don't seem to conserve energy at all. In addition, stuffs can exit the portal towards a different direction than it came in. This means that the conserved momentum was relative to the entry portal rather than the room, so the cube just plopping out would violate the portal's conservation of momentum. Taking these into account, the in-game rules seem to support the former instead. However, this issue was not adressed in both games(maybe we'll see it in Portal 3?)<br>But yeah, extra rules may come into play given the changed circumstances<br>Another version of the riddle is where two portals come crashing into a cube straight in the middle. What would happen?,(reply>), +Revi M Fadli "The problem," meaning what, exactly?