{
  description = "ECP5 toolchain template project";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
  };

  outputs = inputs@{ nixpkgs, flake-utils, ... }:
    let
		python-overlay = import ./python.nix;
      systems = [ "x86_64-linux" "aarch64-linux" "aarch64-darwin" "x86_64-darwin" ];
      forAllSystems = function:
        nixpkgs.lib.genAttrs systems (system: function (
          import nixpkgs {
            inherit system;
            config.allowUnfree = true;
            overlays = [
				python-overlay
            ]; 
          }
        ));
    in {
      packages = forAllSystems (pkgs: {
        sim = import ./sim/package.nix pkgs;

      });
      devShells = forAllSystems (pkgs: {
        default = pkgs.mkShell {
          packages = with pkgs; [
            (python3.withPackages (ps: with ps; [ 
              amaranth
            ]))
            yosys
            nextpnr
            # simulators
            iverilog
            verilator
            # support package
            trellis
            # loader
            openfpgaloader
            ecpdap # easier to poke probes.
          ];
        };
      });
  };
}