Okay, I've figured out the general approach for each of the three stages, with some help from elsewhere online. Unfortunately with the third and final round I feel like giving up. I've been playing with a controller, which makes precise aiming somewhat difficult. And this is particularly needed for grappling the energy weapons that the boss shoots, which you then must shoot back at him.

But despite that, I set it the level on easy and got really far on one playthrough, counting at least 35+ direct hits (where I can see his green blood gushing out) using his energy weapons on the 3rd round of the final boss. 35+ hits seems excessive, and it gets boring and eventually I died. Does it really take so many hits on the final boss? Am I doing something wrong?

I felt like I copped out after finally giving in after so many levels and lowering the difficulty to easy after several attempts at the last level. But if it really takes so long to kill the final boss, I feel like I'm wasting my time and it's tedious. I'm tempted to give up and say fuck the game, even though I also want to feel like I've finished it.

Any thoughts?

Just finished Capsized, playing on Normal.
I don't thing the 3rd phase of the last boss needed so much (35) hits.
As far as I'm concerned, the star crystals take down his shield for a brief time, where you have to nuke him. Rocket launcher works nicely.

Just follow the youtube walkthrough if you are stuck.