The headline: Bass Invaders works on Steam Deck
The detail:
With some help from friends (thanks Em & Sina!) I've been able to test Bass Invaders on the Steam Deck. It basically works (if you knew how some of the backend worked you'd be as surprised as I am). There are a few caveats and recommendations for the best experience.
At the default resolution (1280x800) some of the menu elements overlap a little bit. It looks best at fullscreen 1280x720 resolution, which you can change in the Options menu.
Performance is generally good. The game runs on high settings at around 60fps. There don't seem to be any issues with sound or input latency. All of the text and button hints etc are readable.
Using the game's web browser to search for new music works ok but is a little clunky. The game has a built in virtual mouse, or you can use the Deck touch screen, but to use any text boxes (e.g. search box) you'll need to manually bring up the Deck virtual keyboard (Steam button + X). I'm looking into what I might be able to do to improve the text box behaviour in a future update.