さらに遊ぶ

星がクルクル回るアニメーション

#lang frtime
(require
 frtime/animation)

(define long 50)
(define short 20)
  
(define time (- milliseconds (snapshot (milliseconds) milliseconds)))

(define (star x)
    (build-list 10
                (lambda (n)
                  (let ([radius (if (even? n) short long)]
                        [angle (+ (/ (* pi n) 5) (/ x 300))])
                    (make-posn (* radius (sin angle)) (* radius (cos angle)))))))

(display-shapes
 (list
  (lift-strict make-solid-polygon (lift-strict star time) mouse-pos "yellow")
  (lift-strict make-polygon (lift-strict star time) mouse-pos "gray")))

lift-strictの使いどころが今ひとつ分からない。