move it from downloads do applications
I presume you are on Mac? When all else failed, this is how I got it to open for me, it might work for you. Open up the "Terminal" application. Then find "Submachine universe" in your files. Right click it and a list of options appears. Click "Show package contents". A folder called "contents" should appear, inside that folder should be another called "MacOS". There should be only one file in there called "Flash player". Drag that into your "Terminal" window and then press enter. Submachine universe should start up with no issues. And then, if you ever wish to play it again, you don't need to do that full song and dance every time. After your first time doing this, you need only press up while in terminal to see what should your most recent command, opening submachine universe. From there press enter and it should start up again.
subnet_mac.swf is a file included in your download of submachine universe. Read the other file "Mac OS Troubleshooting.txt" and will tell you how to open it. I cannot guarantee it will work, as personally, I have had issue with this version working. However it is an alternative you should try.
Also, i'll say it again, I, me personally, have never had any issues when opening the game using the method I previously described. In fact it is how I play all of the submachine games I have downloaded from Mat. I have never had issues with them either. So I don't know what to say. I wouldn't even know what to look for to figure out what is different between our computers that is preventing you from doing things this way. My only suggestions would be perhaps check your version of flash player and maybe restart your computer. I know for a fact, that left on long enough, Mac will has weird issues that will disappear when turned off and on again.
Oh yeah it works !
Thanks to you I have created a start.command file in the "submachine_universe_mac" folder with the following 3 lines script:
#!/usr/bin/env bash
BASEDIR=$(dirname "$0")
"$BASEDIR"/subnet_mac_osx.app/Contents/MacOS/Flash\ Player
chmod 755 start.command