Great game!
The first thing that caught my attention were the multiple control schemes you have. I really enjoyed the mouse movement, even thought I would like the ship to move a little faster in that mode.
The graphics where really nice and I enjoyed the story. I would have made the dialogue boxes a little bit more transparent though. Sometimes the pirate captain was speaking and blocked the view on some projectiles.
And as pretty much all of the other commenters already pointed out: The limitation was very well integrated!