Great game, could have been a little harder.
The invuln buff makes the last boss a piece of cake. For those having trouble here are a few tips.
1: Avoid the tiny worms, save them for later as they give you health.
2: Never fully extend out of the planet. Best way to attack is to barely come out of the planet on your side almost. This makes it hard for them to hit you and you can hit them more than once in one go.
3: For the robo worms, hope for an invuln buff and then just circle around the middle of the sun.
4: The only time you should extend completely out are for any form of extractors and the jet soldiers.
5: I upgraded attack first and didn't even bother with speed, kinda useless but I didn't get it so I don't really know.
Pretty easy once you get the hang of it.