I had forgotten that Apogee Software made a sidescrolling shoot-'em-up -- one with '90s-rific pre-rendered 3D graphics, no less. That's more to do with my terrible memory and general cluelessness when it comes to the genre than a statement about the quality of Stargunner.
The game has been freeware for quite a few years, at this point, but there's something about adding these titles to your library on a familiar digital distribution service that makes them seem somehow better. GOG.com is hosting Stargunner, should you want to give it a try.
While the site has your attention, there's also a decent sale on Square Enix games. Look for 60 percent off Startopia, Thief, Soul Reaver, and freakin' Total Overdose, to name a few.
What are you about to get yourself into? Here's a "longplay" by YouTube user cubex55: