I can't seem to open this file.
I've never heard of this file extension. Please advise. Thanks.
Mastermind Classic was made with Unity. 1- Unzip the file. 2- Now you have 3 folders: _Data, .exe and .ddl; They must be stored together in the same folder! 3- Double click on the .exe file. If you still have problems I advise you to use the itchio app; you can download the app from the itchio frontpage. Hope this helped.
In case someone else has the issue: 7z is a file compression extension from a program called 7zip. You can download it for free to unzip the folder. Just google it, its actually a very handy free tool that I would also recommend installing anyway :)