(unit/sig (startwin makecolor setpixel seq width height)
  (import plt:userspace^)

  ; Sequence Operator
  (define (seq a b) (begin a b))
  
  ; Window Size
  (define width 500)
  (define height 500)
  
  ; Make a width x height frame
  (define frame (make-object frame% "Mandelbrot" #f width height))

  ; Make the drawing area 
  (define canvas (make-object canvas% frame)) 

  ; Get the canvas's drawing context 
  (define dc (send canvas get-dc))

  ; Set the drawing color
  (define (setcolor color)
    (send dc set-pen (make-object pen% color 1 'solid)))

  ; Make a color out of an (r,g,b)-value
  (define (makecolor r g b)
    (make-object color% r g b))

  ; Set a point on the canvas in the specified color
  (define (setpixel x y color)
    (setcolor color)
    (send dc draw-point x y)
    #t)

  (define (startwin)
    (send frame show #t)
    #t)
)