GTA: Bloons Tower Defense 2
They look like harmless balloons, but they are not harmless at all. What is even worst is that these things are aliens trying to take over the world. They would not stop till they takeover the world. Your mission would be to pop up all those balloons. You don't want any of these balloons to reach the other end as that would be bad for you. There are several arsenals that you can use depending on the money you got. you earn money from popping these guys. You can upgrade your tower twice each as that would help you to ward off those balloons.