What about adding a very simple Tower Defense game where you have to defend your boosts from the ants. It wouldn’t work if you weren’t on the defense screen. If ants got through your Defenses than it would subtract your boosts like normal. The longer you stayed on screen the bigger the rewards and the damage to your boosts. You could build towers from things you get from the ants (Ant bits/parts?) instead of using coins and whatnot. it would be a different way to keep boosts while your away.