How much linux is required for the phone to run?

[overdrawnfettuccine]

How much boot/init knowledge is required? I absolutely would like a touchscreen and either wifi or a modem with 4g capabilities/SMS.
Would it have enough CPU power to run a basic rougelike game written in C at 60fps? Things simple enough that the nes/snes can do with pixels instead of tiles which make those consoles life easier

Ahh, I see. There are beefier AVR microcontrollers that can probably do what you want, but the ATTIny85 is not it. I would look at some of the higher end ATmega family.

Though, I'm starting to think you'd be better off writing such things as apps for Linux on the PinePhone. Wifi/4G support can be accessed easily that way, and you get full access to high-quality game frameworks like SDL2. Why reinvent the wheel, after all? You can write it in C, just like in microcontrollers/arduino. Many applications in Linux are.

It's more fun when it's bare metal. I'm sure I can easily figure out how to manage the screen and I can live without sound. Input probably not too terrible. However networking is outside of my realm unless I can access it through a library or AT commands.