also, it's impossible to lose once you get past a certain point. your health is just too high, and buying lives is cheap. 9000 gold essentially refills your 200,000 health bar. also, space is going in the wrong direction. it looks like the ship is moving backwards.
better way to beat level 5: load up on tauren, centaurs, ghost armors, black knights, and just knock the little goblin back. worked for me, he never got past his own castle.