If you pay $12 or more for the game, you get an artpack with it. Maybe that'll have what you're looking for.
Click on "Download", extract the zip file somewhere, and double click the .exe. Simple as that.
The game refuses to boot on Steam Deck through Proton for me. I have tested Proton 7.0-6, GE-Proton7-49, and Proton Experimental. Game plays fine through browser, though.
It works now, thanks!
For some reason, the download link for the standalone version doesn't seem to work.
I've tried downloading another game and it downloaded just fine, so I know it's not my internet.