Hexagon can't coexist with Start

[daviddeutsch]

Kind of the same issue as thefifthmatt/windmill-client#28 but it actually works with the End marker, just not the Start marker

[aren227]

That's because start marker is a rule assigned to the vertex. Hexagon is also a rule can be assigned to the vertex. But the problem is currently each vertex can only have one rule. So they can't coexist.

Maybe I should change the code so that each vertex can have more than one rule.

[daviddeutsch]

Yeah, in this case, I think that's justified because it's literally a feature that is used in a puzzle in the game.