Player 1 (West) to play
West should prevent East from winning on East's upcoming turn.
Only one choice keeps West in the game for another turn.
West will lose immediately with any other turn. If West does not catastrophe the reds in East's home, East will win on their turn by moving (or green teleporting) g3 to West's home and calling catastrophe. With their reds destroyed, East can still destroy West's home, but only by abandoning their own home and making the game a draw. The red catastrophe can only be achieved with the yellow sacrifice that starts turn 1 above.
West must use the second movement action to discover a g2 system, which they can only do with the g1 in system 5. Otherwise, a g2 piece (formerly the star of system 3) will be in the bank for East's turn, and East could simply build g2 in West's home and call catastrophe for the win.
Of course, East can still achieve a draw by moving or green teleporting their g3 to West's home. I have not worked out who would win if East continues trying to win.
This game was played between capi3101 (West) and Stevie Sasquatchie (East) as part of Homeworlds Live Winter League 2021. It is game 86 on HWL. capi3101 either resigned or ran out of time in the pictured position.
Bruno Curfs noticed this interesting position and suggested it as a puzzle.