(define smash-count 8)
(define smash-scale-factor 0.5)
(define smash-minimum 0.2)
(define (smash-kick) (vector (- (flxrnd) 0.5) 1 (- (flxrnd) 0.5)))

(collisions 1)
(gravity (vector 0 -1 0))
(ground-plane (vector 0 1 0) 0)

(define (smash-sub n p sz)
  (if (< n 1) (list) (cons (let ((s (build-sphere 15 15))) (begin
    (push)
    (grab s)
      (colour (vector 1 1 1))
      (scale (vector sz sz sz))
      (translate p)
      (translate (vector (flxrnd) (flxrnd) (flxrnd)))
    (ungrab)
    (pop)
    (active-sphere s)
    (set-mass s (* sz sz sz))
    (kick s (smash-kick))
    (list s sz)
  )) (smash-sub (- n 1) p sz)))
)

(define (smash b)
  (if (< (head (tail b)) smash-minimum) (list) (let ((smashed (list)))
    (grab (head b))(let ((pos (vtransform (vector 0 0 0) (get-transform))))
      (ungrab)
      (set! smashed (smash-sub smash-count pos (* smash-scale-factor (head (tail b)))))
    )
    (destroy (head b))
    smashed
  ))
)

(define (make-balls count)
  (if (< count 1) (list) (begin
    (let ((s (build-sphere 15 15))) (begin
      (push)
      (grab s)
        (colour (vector 1 1 1))
        (scale (vector  1 1 1))
        (translate (vector (* 10 (- (flxrnd) 0.5)) (* 10 (+ (flxrnd) 0.5)) (* 10 (- (flxrnd) 0.5))))
        (active-sphere s)
        (set-mass s 1)
      (ungrab)
      (pop)
      (cons (list s 1) (make-balls (- count 1)))
    ))
  ))
)

(define (update bs)
  (if (empty? bs) (list)
    (if (has-collided (head (head bs)))
      (append (smash (head bs)) (update (tail bs)))
      (cons (head bs) (update (tail bs)))
    )
  )
)

(define balls 0)
(set! balls (make-balls 10))

(every-frame (set! balls (update balls)))