I really love this game.
I report one bug :
I was probably on my last jump before the mothership, but I wanted one more to maximise my health (23 turns left, and probably, the last jump would have been a 23 turns one). So I waited a little to let the mothership take distance from me. To be sure, I waited until it remains 27 turns (the music ended). Then, the bug appears when I begin the jump : this one was in 0 turn ... the portal appeared directly on the first turn. I was below rank 20, and I try to have more than 20 and the bug desappear.
I have a tip : when I are shot, your rank decrease to 3 points. So you can try killing lots of ennemies and stay below 20 on rank, but make sure you have enough health.
One more thing : the mothership is really hard to beat. Even with my tip, I have something like 96 energies, 16 health, the powerfull shot, the powerfull punch and 3 range to move ... and I cannot beat him. So let us choose the difficulty ... this one should be the hard one. For the easy one, make the boss with less ennemies ? or less bullet ? or something less overwhelming.
anyway, I can't wait for the final version of this game. Good job.