It looks like one of the files getting deployed to OSX on Steam is borked (launcher script, specifically). We’re working to get this fixed, but in the meantime you can manually replace the contents of the following file: ~/Library/Application Support/Steam/SteamApps/common/spacechem/SpaceChem.app/Contents/MacOS/SpaceChem with the contents of the following file: http://www.zachtronicsindustries.com/spacechem-launcher.txt and then, if it still crashes, running [...]
Useful Links