// FSM for a Red Light, Green Light game with two spaces.
// Moving during a red light puts the player back at the start.
// Inputs:
//  - M: player tries to move forward or not
//  - L: state of the light (1 = green, 0 = red)
// Outputs:
//  - W: player win (if successfully reached second space)
module light_game (input  logic clk, reset, M, L,
                   output logic W);

  // State Encodings and Variables
  enum logic [1:0] {Start, Mid, Win} ps, ns;

  // Next State Logic (ns)
  always_comb
    case (ps)
      Start: ns = (L & M) ? Mid : Start;
      Mid:   ns = (L & M) ? Win : (M ? Start : Mid);
      Win:   ns = M ? Start : Win;
    endcase

  // Output Logic
  assign W = (ns == Win);  // alt: ((ps == Mid) & L & M) |
                           //      ((ps == Win) & ~M)

  // State Update Logic (ps)
  always_ff @(posedge clk)
    if (reset)
      ps <= Start;
    else
      ps <= ns;

endmodule  // light_game