anchor.diff:          let button = jq $ ("#restart")  
   
           canvas ? width(mazeWidth) ? height(mazeHeight) |> ignore
  +        canvas ? clearCanvas () |> ignore
  +
           button ? click(fun _ ->
               cancel ()
               cancel <- startAnimation canvas
  
positive.code:     let main () =
          printfn "version 1"
  
          let w, h = WORLD_WIDTH, WORLD_WIDTH
          let mazeWidth = w*ROOM_SIZE + (w + 1)*DOOR_SIZE 
          let mazeHeight = h*ROOM_SIZE + (h + 1)*DOOR_SIZE
  
negative.code:     let [<Literal>] DOOR_SIZE = 5
  
      let jq = importDefault<obj> "jquery"
  
      // let renderBox className (x: int) (y: int) (w: int) (h: int) =
      //     sprintf "M%d,%d h%dv%dh%dz" x y w h -w
  