(define distance-between 
  (lambda (col1 row1 col2 row2) 
    (sqrt (+ (* (abs (- col1 col2)) (abs (- col1 col2))) 
             (* (abs (- row1 row2)) (abs (- row1 row2)))))))

(define background-transform 
  (lambda (image n) 
    (let ((width (image-width image)) 
          (height (image-height image))) 
    (image-iterate! image 
                    (lambda (col row) 
                      (let ((cooler (rgb-new 
                     (* (modulo (quotient n 3) 256) 
                        (/ 
                         (min 
                          (sqrt 
                           (+ 
                            (* col col) 
                            (* row row))) 
                          (sqrt 
                           (+ 
                            (* (- width col) (- width col)) 
                            (* row row))) 
                          (sqrt 
                           (+ 
                            (* col col) 
                            (* (- height row) (- height row)))) 
                          (sqrt 
                           (+ 
                            (* (- width col) (- width col)) 
                            (* (- row height) (- row height))))) 
                         (sqrt 
                          (+ 
                           (* (/ width 2) (/ width 2)) 
                           (* (/ height 2) (/ height 2)))))) 
                     (* (modulo (quotient n 2) 256) 
                        (/ 
                         (min 
                          (sqrt 
                           (+ 
                            (* col col) 
                            (* row row))) 
                          (sqrt 
                           (+ 
                            (* (- width col) (- width col)) 
                            (* row row))) 
                          (sqrt 
                           (+ 
                            (* col col) 
                            (* (- height row) (- height row)))) 
                          (sqrt 
                           (+ 
                            (* (- width col) (- width col)) 
                            (* (- row height) (- row height))))) 
                         (sqrt 
                          (+ 
                           (* (/ width 2) (/ width 2)) 
                           (* (/ height 2) (/ height 2)))))) 
                     (* (modulo n 256) 
                        (/ 
                         (min 
                          (sqrt 
                           (+ 
                            (* col col) 
                            (* row row))) 
                          (sqrt 
                           (+ 
                            (* (- width col) (- width col)) 
                            (* row row))) 
                          (sqrt 
                           (+ 
                            (* col col) 
                            (* (- height row) (- height row)))) 
                          (sqrt 
                           (+ 
                            (* (- width col) (- width col)) 
                            (* (- row height) (- row height))))) 
                         (sqrt 
                          (+ 
                           (* (/ width 2) (/ width 2)) 
                           (* (/ height 2) (/ height 2))))))))) 
                      (cond 
                        ((>= (distance-between col row (* .25 width) (* .75 height)) (*  .2 width (/ width height))) 
                         cooler) 
                        (else 
                         (rgb-complement cooler))))))))) 
                         
                    
                   


(define make-spiral 
  (lambda (image n) 
    (let ((width (image-width image)) 
          (height (image-height image)) 
          (distance (/ (image-width image) 50))) 
      (begin 
        (define turtler (turtle-new image)) 
        (turtle-teleport! turtler (* width .75) (* height .25)) 
        (turtle-face! turtler 90) 
        (turtle-down! turtler) 
        (turtle-set-color! turtler (rgb-complement (rgb-new (modulo (quotient n 3) 256) (modulo (quotient n 2) 256) (modulo n 256))))

        (let kernel ((count 0)) 
          (cond 
            ((>= count (+ 3 (modulo n 15))) 
             image) 
            (else 
             (kernel (+ count 1)) 
             (turtle-forward! turtler (* distance count 1.3)) 
             (turtle-turn! turtler (+ (modulo n 70) 50)))))))))

(define add-line 
  (lambda (image n) 
     (let ((width (image-width image)) 
          (height (image-height image))) 
    (begin 
      (context-set-fgcolor! (rgb-darker (rgb-complement (rgb-new (* .9 (modulo (quotient n 3) 256)) (modulo (quotient n 2) 256) (* 1.1 (modulo n 256))))))

      (image-draw-line! image 0 (* .2 height) (* .45 width) height) 
      (image-draw-line! image 0 (* .2 height) (* .40 width) height) 
      (image-draw-line! image 0 (* .2 height) (* .35 width) height))))) 
                   


(define make-image 
  (lambda (image n) 
    (begin 
      (background-transform image n) 
      (make-spiral image n) 
      (add-line image n))))