#lang racket
 
(require 2htdp/universe 2htdp/image lang/posn)
 
(struct world (posn1 posn2 posn3 posn4))
 
(define *hoshida* .)
 
(define *background* (empty-scene 480 480))
 
(define (place-hoshida w)
  (place-images (make-list 4 *hoshida*)
                `(,(world-posn1 w) ,(world-posn2 w) ,(world-posn3 w) ,(world-posn4 w))
                *background*))
 
(define (place-hoshida-on-tick w)
  (let ((r (exp (* 0+i 1/28)))
        (posns `(,(world-posn1 w) ,(world-posn2 w) ,(world-posn3 w) ,(world-posn4 w)))
        (convert 240+240i))
    (let ((z (map (lambda (i)
                    (+ (* r (- (+ (posn-x i) (* 0+i (posn-y i))) convert)) convert))
                  posns)))
      (apply world
             (map (lambda (x)
                    (make-posn (real-part x) (imag-part x))) z)))))
 
 
(big-bang (world (make-posn 360 240) ;; 座標初期値
                 (make-posn 240 360)
                 (make-posn 120 240)
                 (make-posn 240 120))
  (on-tick place-hoshida-on-tick) ;; ここで単位時間毎に座標データを更新する
  (to-draw place-hoshida))

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