;;; Scheme Recursive Art Contest Entry
;;;
;;; Please do not include your name or personal info in this file.
;;;
;;; Title: Get DeoxyRiboNucleated with Exactly 255 Scheme Tokens
;;;
;;; Description:
;;;    Random DNA.
;;;    Always a different sequence
;;;    One is surely yours.
(define (line sx sy ex ey)
  (penup)
  (goto sx sy)
  (let ((x_diff (- ex sx)) (y_diff (- ey sy)))
    (if (= 0 x_diff) ()
    (begin
      (setheading (- 90 (* 57.2958 (atan (/ y_diff x_diff))))) 
      (pendown)
      (forward (sqrt (+ (* y_diff y_diff) (* x_diff x_diff))))
    ))))

(define (v_dna lx_start lx_end rx_start rx_end curr_y offset n)
  (cond ((< curr_y -300) ())
        (else (let ((col (abs curr_y)) (col2 (max 0.4 (abs (sin (/ curr_y 2))))) (val (abs (sin (/ curr_y 50)))))
                (if (< (modulo col 25) 7) 
                  (begin
                    (if (= n 0)
                      (define n (random 5)) ())
                    (define pt (/ (+ rx_start lx_end) 2))
                    (color  
                      (cond 
                        ((= n 3)
                         (rgb 0.1 0.1 col2))
                        ((= n 1) 
                         (rgb 0.1 col2 0.1))
                        ((= n 2)
                         (rgb col2 0.1 0.1))
                        (else 
                         (rgb col2 0.35 0))))
                    (line lx_end curr_y pt curr_y)
                    (color  
                      (cond 
                        ((= n 1)
                         (rgb 0.1 0.1 col2))
                        ((= n 3) 
                         (rgb 0.1 col2 0.1))
                        ((= n 2)
                         (rgb col2 0.45 0))
                        (else 
                         (rgb col2 0.1 0.1))))
                    (line pt curr_y rx_start curr_y)
                    )
                  (define n 0))
                (begin
                  (color (rgb 0 (- 1 (/ col 450)) (- 1 (/ col 350))))
                  (line lx_start curr_y lx_end curr_y)
                  (color (rgb 0 (- 1 (/ col 350)) (- 1 (/ col 450))))
                  (line rx_start curr_y rx_end curr_y)
                  (v_dna (+ offset (* 50 (- val))) (+ 15 offset (* 50 (- val)))
                         (+ offset (* 50 val)) (+ 15 offset (* 50 val)) (- curr_y 0.1) offset n)
                  )))))

(define (draw)
  (text 'DNA) 
  (v_dna 170 180 180 170 300 200 0)
  (v_dna 170 180 180 170 300 -200 0)
  (exitonclick))

; Please leave this last line alone.  You may add additional procedures above
; this line.
(draw)