but when a rotation acts on the set of offset classes, (0,1) gets swapped with (1,0) The rail-containing blueprint with offset of (0, 1), as well as non square ones, will never be fully rotationally symmetrical. So there is no need to change it's class - invalid cases can be just skipped, so you ca...

Nothing violates the "rails can't be offset by 1 tile" rule. Blueprints will not change their "offset class" when rotated. The problem is simply this: Factorio blueprint tiling problem.png Both blueprints are perfectly tileable. They are essentially the same. The only difference ...

In other words, the grid must be divisible by 2, but not by 4. That's not true, see the rails I posted here: https://forums.factorio.com/viewtopic.php?p=504154#p504154 They're 28x28, divisible by 2 and 4. What you can't do is have the tracks setup in such a way that it would be possible to place on...

The problem occures when the gap between rails and the size of the blueprint divided by two have a different parity, which is not so rare case. The reason is that blueprint tile border cannot pass through the midle of the rail, since the rail cannot be built on the center of the map (rather weird re...