Here’s something that will sound like an obvious truism to some and opaque to others: the decision space of a board game is derived from its restrictions, not its permissiveness.
Hold up, Morpheus, what do you mean by that? Well, I mean that nothing is permitted until the rules explicitly announce that something is possible. Anything else would be require a ten-volume rulebook, because unless somebody spelled out instructions to the contrary, you could do anything you wanted at any time — which, incidentally, is pretty much how my friend Geoff plays board games. Since that’s untenable for anybody who hasn’t resigned themselves to repeatedly explaining that, no, you cannot teleport across the map and demolish all my armies with one action, the clearest rules start from scratch. Here are the phases. Here’s what it means to move. Here are the steps you follow every time you undertake an action. Nothing exists beyond that framework.
Europe Divided, designed by David Thompson and Chris Marling, is a fascinating look at what happens when you break the rules until they hardly matter.