Thanks for the feedback! Actually, every meteor spawn at the top of the screen, but if a meteor pass by a side of the screen without being destroyed, the same meteor will respawn on the opposite side (example: if a meteor pass by the left border of the screen, he will apear again in the right side, so you can actually see them coming!). I know it's not a explained feature in the game, but it's because we hadn't time to make a tutorial screen, so sadly the game ended up being hard and confusing...