May be a coincidence, but it stopped launching for me too. Worked Monday and Tuesday, yesterday I didn't try to play, today it didn't work.
Tried:
- running "verify integrity of game files"
- forcing Proton,
- clearing shader cache
- attempted various launch options, like vulkan, fullscreen, and windowed
- update all flatpaks (since I installed steam through flatpak)
- reboot
I don't have much experience using srcset but since you are still waiting for an answer... I'll point you to what is stated in MDN's docs.
According to that, you use a "media condition" when the image is displayed in different sizes. Their example
And you use 1x, 2x, etc (like your examples) when the image will occupy the same physical size.