Thanks for playing~! I'm afraid the game isn't as intuitive as we would have liked. The goal is to sling farm animals through portals before monsters spawn out of the portals. If the monsters spawn, you can slingshot them through a portal to get rid of them. Monsters will try to eat your livestock and people, and if you run out of people, you lose. You can get more lives, though, by dragging one of each farm animal to the house on the far right that says 0/3 above it.
Anyway, appreciate your feedback! Thanks for checking it out :D