(define pi (* 2 (acos 0)))

(define res 200)

(define data
  (letrec 
      ((delta (/ (* 2 pi) res))
       (vect (make-vector res))
       (iter
        (lambda (q)
          (if (< q res)
              (begin
                (vector-set! 
                 vect q
                 (cons (cos (* q delta)) 
                       (sin (* q delta))))
                (let ((ev (eval '(iter (+ 1 q)))))
                  ev))))))
    (iter 0)
    vect))

(define draw-circle
  (lambda (radius)
    (letrec
        ((iter
          (lambda (q)
            (if (< q res)
                (begin
                  (draw-line
                   (* radius (car (vector-ref data q)))
                   (* radius (cdr (vector-ref data q))))
                  (iter (+ 1 q)))))))
      (draw-move radius 0)
      (iter 0)
      (draw-line radius 0))))

(define steps 8)

(define circles
  (lambda (maxrad)
    (letrec
        ((iter
          (lambda (q)
            (if (< q maxrad)
               (begin
                 (draw-color 0 (/ (* 255.0 q) maxrad) 0)
                 (draw-circle q)
                 (iter (+ q steps)))))))
      (iter 1))))

(circles 100)