Thank you for reporting this issue.
I also encountered the same error message "PixelAfterAll is damaged and can't be opened" when trying to run the .dmg downloaded from itch.io. Rebuilding didn't resolve the issue, although interestingly, the file runs without errors before uploading to itch.io.
After various tests, I found it can be launched using these commands (based on a YouTube tutorial: https://www.youtube.com/watch?v=DgEA6qu4kYc):
% sudo spctl --master-disable Password: Globally disabling the assessment system needs to be confirmed in System Settings. % xattr -cr /Applications/PixelAfterAll.app
While this is not an ideal solution, it does allow the application to run.
I'll be working on improving this so the app can launch without these error messages in future updates.