### Ubigo (pseudo-toroidal Go) Go forum

12 replies. Last post: 2018-03-04

Ubigo (pseudo-toroidal Go)
• Luis BolaNos at 2018-01-30

I think toroidal Go is a great idea but find it quite confusing to play. Ubigo is a related variant that I prefer.

In Go, every edge point is connected to another two. In toroidal Go, every edge point is connected to another three. In Ubigo, every edge point is connected to all other edge points. It feels similar to games like Kropki and Rin, but, unlike in those, being connected to the edge of the board isn’t enough to make life. It just means it will take much longer for your group to get into trouble, but it eventually will, and you can’t use the edges to make eyes.

On tiny boards, the game is guaranteed to end in a whole-board seki. On smallish boards, it’s about putting yourself on the strong end of an eye-vs-no-eye capturing race. On reasonably-sized boards, you get an involved struggle for center territory.

I’d love to have this variant implemented here.

• ypercube ★ at 2018-01-30

What do you mean with " In toroidal Go, every edge point is connected to another three"?

There are no edge points in Toroidal Go and every point is connected to exactly 4.

• Luis BolaNos at 2018-01-31

As you know, another way to describe toroidal Go is to say that it is just like Go, with the exception that every edge point not in a corner is additionally connected to an edge point in a straight line perpendicular to the edge to which it belongs, and every corner point is additionally connected to the two closest corner points.

(I should have said: “In toroidal Go, every edge point is connected to another three, except corner points, which are connected to another four”.)

• ypercube ★ at 2018-01-31

I think you are still either confused or not describing it correctly.

Every edge (not corner) point is connected to 3 other point (in normal and toroidal Go) and 1 more point is toroidal Go (which we can find with a straight line, perpendicular ..., that’s correct).

Every corner point is connected to two other points (in normal and toroidal Go) and 2 more points in toroidal Go.

So every point in toroidal Go is connected to exactly 4.

• Luis BolaNos at 2018-01-31

I think I’m describing it correctly. When I say “In toroidal Go, every edge point is connected to another three, except corner points, which are connected to another four”, “another three” obviously means “another three edge points”, and “another four”, “another four edge points”.

• David Milne at 2018-01-31

If you have a paper 19x19 go board and bend it into a cylinder so that the right side meets the left side, you would have an 18x19 playing area. Is that right?

• Carroll ★ at 2018-01-31

Yes and if you connect top circle to bottom one, you get 18x18 toroidal Go board...

@Luis, your description is correct but why speak of edges on a torus which is edge free? You simply have all points connected to its four cardinal neighbours, I don’t see the added value to make it more complicated?

Is it a way to explain Ubigo, do you have pointers to its description?

• Luis BolaNos at 2018-02-01

Carroll, yes, it’s a way to point out how toroidal Go and Ubigo are related. But it’s also a valid way to describe toroidal Go, considering that you most certainly won’t play it on a real torus.

I haven’t seen Ubigo described anywhere else.

• Hjallti at 2018-03-04

The description is obviously incorrect or rather trivially correct. The are no edge points. So every edge point is connected to 7 others including a monkey shaped center point. The last sentence being as correct as the statement of Luis.

• William Fraser at 2018-03-04

I think that what Luis is talking about makes sense.  We’re going to be comparing the 19x19 flat go board to the 19x19 toroidal go board.

Let us define the points A1-A19-T19-T1-A1 (72 points in all) as edge points.  And further define the 4 points A1, A19, T19, and T1 as both edge and corner points.

Then, on the flat board, each edge point borders 3 points, 2 of which are edge points.  And each corner point borders 2 points, each of which is an edge point.

On the toroidal board, each point borders 4 points, with the edge points bordering 3 edge points and the corner points bordering 4 edge points.

For example, H1 borders H2 (not an edge point) along with G1, J1, and (only in toroidal go) H19.

And A1 borders A2 and B1 (both edge points) and in toroidal A19 and T1 (also both edge points).

For Ubigo, we define all edge points as connected, and thus have 71 neighbors (in the case of corner points) or 72 neighbors (for the rest of the edge points).

• William Fraser at 2018-03-04

And David, we aren’t merging the left and right sides, we are placing them adjacient to each other (with lines connecting them) so that we still have a 19x19 board.

• ypercube ★ at 2018-03-04

I’ll “change” the subject to the original attempt, to describe this new variant: Ubigo:

If I understand right, then all edge and corner points are inter-connected, so the topology on the “borders”, which are no longer borders any more changes a lot.

I would assume that play would quite similar to Torus Go in some aspects, like trying to create eyes in the middle but also quite different in other aspects because the topology is very different at the edges.

Include game board: [game;id:123456] or [game;id:123456;move:20] or [game;id:123456;move:20;title:some text]