Arimaa Forum - Print Page


    
      
        Arimaa Forum
        (http://arimaa.com/arimaa/forum/cgi/YaBB.cgi)
      

        Arimaa >> General Discussion >> Endgame Puzzle 4
        
(Message started by: jdb on Sep 4^th, 2008, 12:00pm)

Title: Endgame Puzzle 4
Post by jdb on Sep 4^th, 2008, 12:00pm

The silver rabbits must find a way to sneak through.

1w Rc1 Cf1
1b rf7 rg8
2w pass

Link to planning window:
http://arimaa.com/arimaa/games/planGame.cgi

Note: There will always be only one winning move.

Title: Re: Endgame Puzzle 4
Post by arimaa_master on Sep 4^th, 2008, 12:21pm

on 09/04/08 at 12:00:40, jdb wrote:

It looks suspiciously easy at first sight.
(Edit: not so easy at all: I first thought about:
2s rg8s rg7s rg6s rf7w

but it is not good for "not so obvious"

3g Cf1e Cg1n Cg2n Cg3n

and now silver is lost
)

2s rg8s rg7s rg6s rg5e

now gold need two cat moves to defend thus gold can use up to 2 steps to attack/defend with rabbit

3g Cf1e Cg1n Rc1n Rc2e

now the final attack is quite easy to find:

3s rf7w re7s re6s re5s

and now gold has no defence

Title: Re: Endgame Puzzle 4
Post by RonWeasley on Sep 4^th, 2008, 12:43pm

I like how head-to-head rabbits on the fourth rank produce a local zugzwang.

Title: Re: Endgame Puzzle 4
Post by aaaa on Sep 4^th, 2008, 4:00pm

I don't think it's r->h5 as Silver's first move; consider Gold doing C->g4 after that.

Title: Re: Endgame Puzzle 4
Post by arimaa_master on Sep 5^th, 2008, 2:07am

on 09/04/08 at 16:00:42, aaaa wrote:

I don't think it's r->h5 as Silver's first move; consider Gold doing C->g4 after that.

Yes you are right, I considered it already but I didn´t see that local zugzwang mentioned by Ron.

2s rg8s rg7s rg6s rg5e
3g Cf1e Cg1n Cg2n Cg3n
3s rf7w re7s re6s re5w
4g Rc1e Rd1n Rd2n Rd3n

and silver is lost

Now I think I found it!

2s rf7w re7s re6s re5s

that is logical conclusion cause now gold has to defend with cat thus the second rabbit can go freely down the h file.

Others 2s moves cannot be good because gold can always face one rabbit with his one thus winning.

So it is clear that 2s rf7w re7s re6s re5s is only one solution where gold cat has to deal with both silver rabbits (but it is not possible :)).

Title: Re: Endgame Puzzle 4
Post by jdb on Sep 5^th, 2008, 6:34am

on 09/05/08 at 02:07:35, arimaa_master wrote:

Now I think I found it!

2s rf7w re7s re6s re5s

that is logical conclusion cause now gold has to defend with cat thus the second rabbit can go freely down the h file.

Gold still has a few tricks remaining...
3g Rc1e Cf1w Ce1n Ce2n

Title: Re: Endgame Puzzle 4
Post by Fritzlein on Sep 5^th, 2008, 7:29am

on 09/05/08 at 06:34:45, jdb wrote:

Gold still has a few tricks remaining...
3g Rc1e Cf1w Ce1n Ce2n

Oooh, nasty...

2s rf7w re7s re6s re5s
3g Rc1e Cf1w Ce1n Ce2n
3s rg8s rg7s rg6s rg5e
4g Rd1e Re1e Rf1e Rg1e
4s rh5s rh4s rh3s
5g Ce3s re4s Ce2e re3s

You wouldn't think there could be so many subtleties. Silver has to threaten immediate goal on every move, because Silver has no defense to Gold's rabbit. That should limit the options and make it easy to find the win, given that we know there must be a win...

Title: Re: Endgame Puzzle 4
Post by arimaa_master on Sep 5^th, 2008, 10:14am

on 09/05/08 at 06:34:45, jdb wrote:

Gold still has a few tricks remaining...
3g Rc1e Cf1w Ce1n Ce2n

Wow, thats very nice defense complicating things a little bit. However the solution is threaten goal in every move (like was said by Fritzlein) and keeping the silver rabbits separate as much as possible.

This is a solution (as I believe :))

2s rf7w re7s re6s re5s
3g Rc1e Cf1w Ce1n Ce2n
3s rg8s rg7s rg6s rg5e
4g Rd1e Re1e Rf1e Rg1e
4s rh5s
5g Ce3s re4s Ce2e re3s
5s rh4w rg4w
6g re2n Cf2w Rh1w
6s rf4w re3w re4e rf4e

and now I believe that gold cannot stop the goal in one.

Title: Re: Endgame Puzzle 4
Post by Fritzlein on Sep 5^th, 2008, 4:02pm

That's the first position I've seen where a one-step move is winning and all other moves are losing.