ej 3 p2

(define COLOR "black")
(define FONDO (rectangle 350 350 "solid" COLOR))
(define ALTO 350)
(define ANCHO 350)
(define (pantalla F) (place-image F (/ ANCHO 2) (/ ALTO 2) (empty-scene ANCHO ALTO)))
(define COLORs "white")
(define TAMAÑO 40)
(define STAR (star TAMAÑO "solid" COLORs))
(define (tecla n x y event) (cond ((and (string=? event "button-down") (>= (- ANCHO (+ x (/ (image-width STAR) 2))) 0) (>= x (/ (image-width STAR) 2) ) (>= (- ANCHO (+ y (/ (image-width STAR) 2))) 0) (>= y (/ (image-width STAR) 2) ) ) (place-image (star TAMAÑO "solid" COLORs) x y n))  (else n) ))
(define (backspace n k) (cond ((key=? k " ") FONDO) (else n) ) )


(big-bang FONDO
          (to-draw pantalla)
          (on-key backspace)
          (on-mouse tecla)
          )