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。