JasonEmery: Hello! I'm the developer of Tyrian.
It would take a while to explain the story, such as it is. Let's just say it's a weird mix between serious issues and complete parody. Ultimately the 'story' is fairly loose as a series of connected events and possibly related data(cubes).
Looking back, it mostly is exploring the results of endless corporate self-justification (both positive and negative intentions). It's a kind of stark realization that nothing is ever completely good but there's always a struggle. And LOTS of shooting! Pew pew!
It's correct that originally it only went up to Chapter 3. 4 and 5 are you saving the galaxy from more possibly terrible things!
There's a lot of subtext around things, some of which I can't say anymore if I've added in my head afterward over the years, frankly.
I will say that it's notable that the Hazudra (your friend with the 'crystal mind') was part of a secret group / race that was trying to protect the universe, which is why he was your friend in the first place. After that, it's all about getting wrapped up in the crazy goings-on outside of the relatively isolated planet of Tyrian (which ironically is very important because of the unexplained non-gravitational minerals it is comprised of - and is further evidence of why you are so important and unique).
In a way, it's hard to comprehend in the same way that, if you -really- were an individual wrapped up in these things, you'd only have a small amount of context.
I liked adding in, at the end, how you realize how you don't want to be a part of that, once you've stopped Microsol. And that the Sol system is thought to be an uninhabited backwater. Little did he know! :D
Most of it is meant to make you laugh and enjoy the game. :D
Huh - this is the second time I've been surprised on GOG by having the developer answer my question personally.