Loosely inspired by Allumwandlung, here's my first attempt at a Binary Homeworlds problem in the same vein as Simple, Monopoly, Inheritance or Insurance Fraud, and Blastdoor.

Graphical representation of the position

Lee (0, g3b2) r1r3g1b1-
Ray (1, r1r3) -y2g3b3
DS1 (y2) b2-r1r3
DS2 (g1) g1g2-
DS3 (g2) y2-
DS4 (b2) r2-g3

The stash contains r2r2 y1y1y1y3y3y3 g2 b1b1b3b3.

Ray's red homeworld is armed to a frankly ridiculous degree, but all for naught: Lee's mini-Doomsday-Machine is almost complete and his victory is assured.

Lee to play and mate in 1. (That is, you must find the unique move which Lee can make, such that no matter what Ray replies, Lee will win on the very next turn.)

  • $\begingroup$ Many thanks to @Sleafar for their Inkscape template! I used BoxySVG to ungroup and drag the pieces around, and the whole experience was super pleasant. $\endgroup$ Commented May 27, 2020 at 21:26

1 Answer 1


I have not played this game before, so I might be very wrong, but I think the way to win is

Trigger an overpopulation in the opposing home system.

And the best way to do that appears to be

Sacrifice the green 2 at DS2 to create two green ships at your own homeworld, triggering a catastrophe and making it a size 2 system.

Which threatens

Sacrifice the yellow 2 at DS3 to move both red ships to Ray's homeworld and Catastrophize it.

  • 2
    $\begingroup$ Good on you for attempting, never having played before! But indeed you are very wrong. :) Lee cannot build red at DS3, because in order to build a ship of color X you must already have a ship of color X in the destination system. (Mnemonic: "Ships have baby ships of the same color.") $\endgroup$ Commented May 28, 2020 at 21:52
  • 1
    $\begingroup$ @Quuxplusone Oops, missed that in the initial rule reading, sorry $\endgroup$
    – Sconibulus
    Commented May 28, 2020 at 21:59
  • $\begingroup$ Was the answer edited? @Quuxplusone's comment does not seem to refer to the current solution . . . I like the current solution, but it's possible to use a different move to accomplish the same goal in the second move. $\endgroup$
    – Cuc
    Commented May 29, 2020 at 12:02
  • 1
    $\begingroup$ The answer was edited ("17 hours ago"). As of this moment, it is correct! $\endgroup$ Commented May 29, 2020 at 15:33

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