I've seen it, it's pretty good! but doesn't quite get to the challenge I'm talking about. Take the mechanic from Mario where the tiles flip, for example. Before you can think of how to introduce the mechanic to the player and subsequently present him with more challenging situations that require more sophisticated strategies, you have to figure out what exactly constitute these challenges and strategies. What layout patterns are too hard/easy, which grid size is too big, too small, too narrow, and what kind of enemies combine well with them, which don't? These things have to be well defined and are then used to create the levels. It's all based on experimentation, and I find that hard.
I guess I'm not talking about "level design" exacly, but an almost invisible step preceding it. You can tell that when someone analyze a game, like the video, they already have the knowledge of what a good level using the mechanic looks like and take that for granted.
Yeah, i get what you mean.
Well, i believe it all comes down to what the player does in the most basic level. In the case of mario everything boils down to jumping and running with him. So i would place a bet that the size of the tiles, the spacing, the timing it rotates, and everything else relating to it is firstly compared to the Mario mechanics.
For instance, rewatching the video, it seems to me that the lenght of mario's jump is th length of the tile, so if he jumps from the middle of a tile directly to another tile, it will land in the middle of it. The time it stays still before rotating is exactly the time it takes to jump, land and run two steps, so the player will always have this window of oportunity of two steps to avoid an error or correct a wrong jump, or something like that. But i'm just speculating and can't really be sure of any of it.
In any case yeah, it is somewhat based on simple experimentation, trial and error, and whatnot. But i believe you can filter down how much, or how far you'll have to trial and error if you have in mind the most basic action the player will be doing the whole game.