Similar to Galaga/Lost Viking, or something I think was called Defender on Sega, it's a scrolling space shooter with some ship customization. I like it. Apparently there were two games by this name, one from 1982 and another from 1996, so this would probably be the 1996 one if not a remake. Found it on GOG, and it's free and neato.
At this time, Benevolens Psittacorum has 21 views for Stargunner spread across 5 videos. His channel published less than an hour of Stargunner content, making up less than 0.11% of the total overall content on Benevolens Psittacorum's YouTube channel.