;Turtles All The Way Down
;
;What lies under Earth?
;A great turtle rests below, 
;On turtles down down.


(define (move-to x y)
	(penup)
	(setheading 0)
	(setpos x y)
	(pendown)
)
; (define (rotate size a)
; 	(penup)
; 	(circle size a)
; 	(pendown)
; )
; (define left-f)



(define (shell _size n x y)
	(define size (/ _size n))
	(define (build-level n p)
		; (define rad (* n size))
		(if (= n 1)
			(circle size)
			(cond
				((= p 0)
					(left 90)
					(forward size)
					(left -90)
					(circle (* (- n 1) size) 22.5)
					(build-level (- n 1) 8)
				)
				(else
					(circle (* n size) 45)
					(left 90)
					(forward size)
					(left 180)
					(forward size)
					(left 90)
					(build-level n (- p 1))
				)
			)
		)
	)
	(move-to x (- y _size))
	(build-level n 8)
)
(define (draw_turtle size x y a)
	(define foot-rad (/ size 5))
	; (define foot-LLen (/ size 4))
	(define foot-RLen (* size 0.34567085809))
	(define (draw-foot n)
		(cond ((> n 0)
				(circle size 22.5)
				(left -90)
				(forward (/ size 4))
				(circle foot-rad 180)
				(forward foot-RLen)
				(right 67)
				; (left 23)
				(circle size 50)
				(draw-foot (- n 1))
			)
		)
	)
	(move-to x (- y size))
	(penup)
	(circle size a)
	(pendown)
	(draw-foot 4)

	(move-to x (+ y size))
	(penup)
	(circle (* -1 size) (- 20 a))
	(pendown)
	; (rotate (* -1 size) (- 20 a))
	(left 110)
	(forward foot-RLen)
	(circle (* 0.34202014332 size) 180)
	(forward foot-RLen)

	(shell (* size 1.01) 3 x y) 
)

(define (turtle_circle size t-size)
	(define (iter a n)
		(cond ((> n 0)
				(draw_turtle t-size (* (cos (radians a)) size) (* (sin (radians a)) size) (+ a 90))
				(iter (+ a 45) (- n 1))
			)
		)
	)
	(iter 22.5 8)
)

(define (iter n m b)
	(cond ((not (= n 0))
			(color (rgb .2 .5 b))
			(shell m 4 0 0)
			(turtle_circle (* m .885) (/ m 12))
			(iter (- n 1) (* m 2.25) (- b .2))
		)
	)
)
(bgcolor "#000000")
(speed 0)
(iter 5 15 1)

; (shell 10 4 0 0)
; (shell 40 4 0 0)
; (shell 90 4 0 0)
; (shell 202.5 4 0 0)
; (shell 455.625 4 0 0)
; (shell 1025.15625 4 0 0)
; (turtle_circle 20 4 0 0 22.5)
; (turtle_circle 45 9 0 0 0)
; (turtle_circle 101.25 20.25 0 0 0)
; (turtle_circle 227.3 43 0 0 0)
; (turtle_circle 512 102.2 0 0 0)