I've never even paid full price for a game since it went to $70.

It sounds like a subsystem of notepad because that's the word used as the modifier.

It's a subsystem of Windows. Therefore, a Windows Subsystem. I don't know what else would make sense. A "subsystem of Linux for Windows" wouldn't make sense. They don't call their other features "Notepad for Windows" or "Defender for Windows."

SMB2: More Of The Chris Pratt Shit You Actually Keep Funding