Not liking the soul shard system. It forces you to use basic units until you can save up a bunch of souls to upgrade, but at that point you have to spend all your gold on basic units to stay afloat until an easy wave comes.
This is actually really neat, and one of the more unique things I've seen on kongregate (yes, far more unique than a lot of those popular games). Four stars from me, and providing source code is just great. It would be really cool to see this implemented in a more fleshed out space exploration game or the like.
For the health bar, if it's shrinking toward the middle, change the registration on the bar instance to the left and not the middle. It will shrink towards wherever the registration point is.
If it's not working at all, that's because you need to call resetHealth(); in your ship's onLoad function.
Meh, 2/5.. congrats on the first game but seriously it wouldn't hurt to make it a little original, all the games people are making are just clones of the shootorials with different graphics..