;; Ripple effect - radial wave distortion from center
;; @param frequency float [1, 20] default 5
;; @param amplitude float [0, 50] default 10
;; @param center_x float [0, 1] default 0.5
;; @param center_y float [0, 1] default 0.5
;; @param decay float [0, 5] default 1
;; @param speed float [0, 10] default 1

(define-effect ripple
  ((frequency 5) (amplitude 10) (center_x 0.5) (center_y 0.5) (decay 1) (speed 1))
  (let* ((w (width frame))
         (h (height frame))
         (cx (* w center_x))
         (cy (* h center_y))
         (phase (* (or _time 0) speed 2 pi))
         (coords (ripple-displace w h frequency amplitude cx cy decay phase)))
    (remap frame (coords-x coords) (coords-y coords))))