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This is the first reporter again. I did some further testing of Gunman Taco Truck on Proton & compared against it running on Windows 7. From that, another Proton-specific issue I was able to confirm is that if you're outputting at an ultrawide resolution (e.g. 3440×1440) the game will unintentionally fill the screen via severely cropping off the top & bottom. To fix this, you'll need to manually change your desktop resolution to your screen resolution's 16:9 equivalent (e.g. 2560×1440) in order to force the game to display properly i.e. with big black bars on the left & right.
Running Gunman Taco Truck under the default version of Proton (4.11-3 at the time of typing this report) meant the game could not even reach its title screen. Using versions 4.2-9, 3.16-9, or 3.7-8--the alternatives available to me--all allowed the game to run to/beyond this point & into actual gameplay. However, music & most sound effects (SFX) did not play no matter how much I toyed with the in-game audio settings, which could only lower the volume of or mute the few remaining SFX. I do not know how to fix this, so I need to rate this game 'bronze'.
Less importantly, this game appears to use borderless windowed mode for its fullscreen implementation & so for some reason the GNOME Shell top bar would not go away. The top bar did not overlap with & cover any bit of the game, but this meant the game had tiny black bars on the left & right. I was able to fix this by installing the extension 'Hide Top Bar' from GNOME Extensions. I do hope more people test Gunman Taco Truck, particularly people with more troubleshooting knowledge than myself.
