They're not saying swapping equal valued variables breaks it. It's when the pointer is the same, using the trick to swap a variable with itself will set the variable to 0.
The trailer is intentionally vague to avoid spoilers. I thought the same thing playing through the game for the first hour or so until I got to a puzzle that made me realize why they built their own engine.
MINOR SPOILERS: Some of the later puzzle mechanics rely on playing with lighting and perspective in a way that seems to me would be difficult to implement in a stock engine.
ah, interesting, will have to buy to see what all the chatter is about :)
I seem to be downvoted to death - the comments weren't meant in a disrespectful way - just wondered why the gargantuan effort with a DIY engine. The game itself looks really interesting.
> ...just wondered why the gargantuan effort with a DIY engine.
Given that Jonathan Blow is in charge of the project, it's almost certainly because existing engines were inadequate for the task.
From what I can tell, Rust is the most ambitious Unity project out there. The Witness is substantially more technically ambitious than Rust. Additionally -from what I read on the Rust devblogs-, the Rust guys spend a large amount of time working around Unity's limitations, missing features, and parts of Unity that are just buggy. (Granted, the buggy stuff generally eventually gets fixed, but until it gets fixed (if it ever does), you have to work around it.)
Actually, I think Frontiers (http://explore-frontiers.com/) might be even more ambitious Unity-using game, but the developer working on it is in over his head. Still, what he's done so far is amazing already.
In regards to them using a law firm in Texas, it may be due to favorable courts there for intellectual property holders. The first article I found about this talks specifically about patents [0], but I wouldn't be surprised if the courts were similarly favorable for other matters of intellectual property.
In a similar vein, the cantor function [1] (also known as the devil's staircase) is continuous and has derivative 0 almost everywhere, but still manages to increase in value.
