;; Define systems here
(setv GRAVITY 5)

(defclass GoalHit [Exception])

(defn apply-gravity [entity entities]
  (when (not entity.fixed)
    (.move entity #(0 GRAVITY))))

(defn apply-collisions [entity entities]
  (when (not entity.fixed)
    (for [ent (gfor enti entities
                    :if (!= enti.id entity.id)
                    enti)]
      (when (.colliderect entity.rect ent.rect)
        (if (= ent.type "goal")
            (raise (GoalHit))
            (let [collision-rect (.clip entity.rect ent.rect)
                  move-x (get entity.total-move 0)
                  move-y (get entity.total-move 1)]
              (when (!= move-x 0)
                (.move entity #((* (if (> move-x 0) -1 1) collision-rect.width) 0)))
              (when (!= move-y 0)
                (.move entity #(0 (* (if (> move-y 0) -1 1) collision-rect.height))))))
        (.ground entity)))))