This game isn't all that hard.
Everyone, the trick is buying only level 1 guns and making a path to where they have to go all the way up then all the way down. After you completed the whole map like that you sell guns and replace them with your stronger gun. Thus making them have to take a forever long path and you will like never lose.
I believe the super strong gun is a tad to strong. To expensive as well.
You need more "splash attack" weapons.
Maybe a fast forward button to watch everything go by 3x faster would be cool since it takes so long sometimes.
Also, if you make a 2nd, I could see you blocking their path. Then they will try to destroy it. I mean THEY ARE MADNESS PEOPLE...they tend to be extremely violent.