;; Posns and Images

;; A Posn is (make-posn Number Number)

;; A List-of-Posns is one of:
;; - empty
;; - (cons Posn List-of-Posns)


;;TODO: write template


;; Define a function 'from-orig' which takes a list of posns and
;; returns a list of numbers
;; each number is the distance from the posn to origin (0 0)
;; example: (from-orig (cons (make-posn 3 4) (cons (make-posn 6 8) empty)))) -> (cons 5 (cons 10 empty))


;; Define a function 'increment-y' which takes a posn and increments
;;  the y-coordinate by 10


;; Define a function 'inc-list' which takes a list of posns and increments
;; all the y-coordinates by 10


;;load the world.ss package

;; Define a scene


;; Define an image ufo by overlaying an ellipse and a circle

;; Define a function 'world-scene' that takes a list of posns
;; and places ufos at those locations into your defined scene


;; finally run your list of posns through this

;; World -> World
(define (world-new list-of-posns)
  (update (world-scene list-of-posns) produce (inc-list list-of-posns)))

(big-bang 600 200 .1 (cons 1 (cons 10 (cons 50 empty))))
(on-tick-event world-new)