OK, this is a weird question here, but I'd like to have a block which is solid to certain players, and not solid to others.
The people to which it's solid should be able to walk over it etc. like they would with a normal block, but the others should pass right through.
This would also be different for different players at the same time, so one is standing on top of it while at the same time someone else falls through it.
Whether or not a player is able to pass through is determined by a boolean value.
But I've got zero clue on how to approach this... anyone knows something?