Thank you (I'm starting the game right now armed with your advice). It seems I found a way to exploit the mechanics in such a way that I never really needed the defense (until the final stages, where I died every time), and so managed to ruin the game for myself. Well well, I'm serial cheeser, what can I say? I'll stick to the narrow path from here on.
I love the sound design of this game. I don't remember what they are called, but you know, the horrible bastards that give off some sort of squeaky balloon sound? Genius.