Problems using nix-gaming as a flake

[makuru-dd]

it is extremely confusing how you want me to install it
as a flake
error: attribute 'inputs' missing

in nix stable way
error: in pure evaluation mode, 'fetchTarball' requires a 'sha256' argument

[fufexan]

You seem to be using flakes, otherwise you wouldn't get the error about sha256.

If you're using flakes, I assume you're familiar with how you can add an input to your system configuration flake. This is no different. You add an input named nix-gaming with the url github:fufexan/nix-gaming.
After that, make sure you have specialInputs = {inherit inputs;}; in your nixpkgs.lib.nixosSystem call, where you define your nixos configuration. Alternatively, make sure you have extraSpecialInputs = {inherit inputs;}; in your home-manager.lib.homeManagerConfiguration call where you define your homeConfiguration.

The readme briefly mentions the instructions, since they are general in the flake world, so I should not need to repeat them here. Feel free to refer https://nixos.wiki/wiki/Flakes#Using_nix_flakes_with_NixOS.