;;; Scheme Recursive Art Contest Entry
;;;
;;; Please do not include your name or personal info in this file.
;;;
;;; Title: the Black Hole
;;;
;;; Description:
;;; I wonder
;;; What inside the black hole
;;; past future or another world

(define (draw)
  	(speed 0)
	(windmill MAX_R)
	(radiation)
	(rings MAX_R2)
  (exitonclick))

(define MIN_R 180)
(define MIN_R2 10)
(define MAX_R 200)
(define MAX_R2 400)
(define STEP 20)
(define STEP2 5)

(define (repeat n func) ; Repeat func k times.
	(if (> n 0)
		(begin 
			  (func) 
			  (repeat (- n 1) func)
		)
	)
)

(define (windmill r)
	(if (or (>= r MIN_R) (>= (- r) MIN_R))
		(begin
			(repeat 45
				(lambda ()
					(pendown)(circle r 180)
					(penup)  (circle r 180) (rt 8)
				)
			)
			(if (> r 0)
				(windmill (* (- r STEP) -1))
				(windmill (* (+ r STEP) -1))
			)
		)
	)
)

(define (radiation)
	(pendown)
	(repeat 120
		(lambda ()
			(pendown) (fd (* 2 MAX_R)) 
			(bk (* 2 MAX_R)) (rt 3)
		)
	)
)

(define (rings r)
	(if (>= r MIN_R2)
	    (begin (goto r 0)
	           (pendown) (circle r)
	           (rings (- r STEP2))
	    )
	)
)

; Please leave this last line alone.  You may add additional procedures above
; this line.  All Scheme tokens in this file (including the one below) count
; toward the token limit.
(draw)