I like the idea that the player gets bigger as time goes on, making it harder to dodge attacks and making you aim differently. Unfortunately, it seems if you make it past the hectic beginning, you can't ever really die, since the enemies don't do enough damage to bring your health low. In particular, the big enemies don't even attack you if you're too big, because they can't get close enough to your "center" to feel like swinging.
With a few tweaks to balance, a score counter, and enemies which get more threatening over time, this could work out quite well. It reminds me of Devil Daggers.
Also, yes, clearly your mouse sensitivity is very low compared to most people. It's not a big deal since I could turn the sensitivity down.