Nice hit effect and that bg music is very spooky -- maybe not high-octane enough for a boss fight in space, but I still liked it :)
I don't think there's any way of dodging attacks from the boss which makes it feel like I'm in less control since my option seems to be to roll the dice until I land on an even number. Maybe a small tweak to this idea would be that attacks don't hit me if the boss is off to the left or right so timing comes more into play? The timing was a cool part of making attacks, so having a way of using it in the defense too could be nice.