Mary Russell

One of the things that drew me to Mark Herman's Ribbit, and made Mary and I so eager to publish it, is that it oddly reminds me quite a bit of backgammon. Backgammon, as regular readers of these blog-things might recall, is my favorite classical abstract. On the surface, there perhaps doesn't appear to be a lot of similarity between the two. Backgammon is after all a game of both luck and skill, while Ribbit is a pure combinatorial abstract. And it isn't as if backgammon has the market cornered on moving, attacking, and blocking, features common to most abstract games.

The key point of similarity to me is that Ribbit is a racing game. The goal isn't to eliminate your opponent's pieces - just as in backgammon, attacking them merely sends them back to the start - or to bottle them up, but to exit the board. The key quirk in the design is that there are five victory spaces upon which the exiting pieces will be placed, and that these spaces are worth different amounts of victory points. You don't need to be the first one to bear off, nor do you need to bear off the most pieces - you just need to bear off the right pieces at the right time.

That being said, getting more pieces to the end zone faster is better than fewer pieces slower, and so one is tempted to look for the quickest and safest route from A to B. Because a jump requires four spaces in a row - two occupied by friendly movers, one occupied by the enemy piece, and one empty space - a piece is safe when there are no empty spaces behind it for a jumping enemy to land on. Relative safety is afforded in the inner-most of the board's concentric circles, and in the outer-most; the attacking enemy movers will need to be within that ring to pull off the jump. Of the two, moving along the outer ring seems better, because your side's entrance spaces are already part of that ring. You can feed your movers up the line without ever exposing them to a jump, whereas moving inward carries with it the risk of your pieces being jumped in transit. 

So, here's a question: why not just do that? Why not just feed your movers in a solid line up along the outside? It takes seven actions to get someone from the outer-most entry space to the exit, and you get two actions on a turn (except the first player, whose first turn consists of one action only). If both players did only this - never deigning to interfere with one another - then the game would end on the first player's twelfth turn, and the first player would win.

That's all well and good for the first player, not so great for the second. But what can the second player do to prevent this? They can't jump the first player's movers. And trying to squeeze a mover or place a blocker in the line will only speed up the first player's advancement, as a piece that executes a jump will effectively moves three spaces in a single go.

What you need is a way to block them that doesn't open you up to being jumped. There are two such points, where the outer-most two rings terminate, forming the line that bears the movers in toward the exit. I'm going to call them anchor points because in this respect they function much like those points in backgammon. Getting one of your movers in one of those spaces can disrupt your opponent's little procession rather dramatically. Here, one of the blue movers is threatening to do precisely that:

What will red do on their go?

If they choose to ignore the threat, simply continuing to move their two pieces in tandem, blue will simply move their piece twice to secure the anchor point:

And let's say that on their next go blue decides to put a blocker on top of that happy little duck, and suddenly red needs to shuffle itself back down the line and around it. All the while blue is gaining in the race. Red doesn't like that one bit, so they're unlikely to let blue get that sweet spot.

So maybe instead, they move their front-most pawn twice, securing the space, but opening a hole in their line in the process:

Now, it's not safe for the blue pawn to insert itself in that opening just yet - it's just going to get jumped - but blue might use one of their two actions to make a threat on the other anchor point.

And this again forces red's hand. Red can't advance their furthest-along pawn without opening up that second anchor space. If red uses both of their actions to advance its other pawn to the first anchor point, that will leave two gaps in the line. That's enough space for the blue pawn and a blue blocker:

This is jump-proof - call it a two-point prime! - and will force the other red movers to venture inward, exposing themselves to all sorts of blue shenanigans. Now, the two red movers already heading for the exit are going to be safe, but unless they manage to get the two three point victory spaces in the center - which is unlikely - they'll need to get a third pawn safely home. 

This doesn't guarantee success for blue; they can't get so focused on blocking red that they neglect to advance in the race themselves. (Which sounds like me playing backgammon all over again!) But it does show how brittle a "safe" strategy can be, and how easy it can be to disrupt. Red in this example would have done better to put some pressure on blue, perhaps threatening to get a red mover in one of blue's "anchor points". It may even have been a better idea to develop some pawns further inwards, in positions that were riskier but afforded more flexibility. By sticking to the outer ring, and focusing solely on advancing their pawns - by ignoring the "jump" and "block" inherent in "the jump, move, and block game" - red gave blue a measure of control over red's own options.

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