Condemned World TD

Mankind had abused the world and now the mother earth wants to get rid of mankind.  Earth has released some of the vile monsters that are willing to kill all humans.  But, mankind is not giving up without a fight.   The game is played via mouse and the idea here is to build some tower defense in the right place.  You can upgrade these towers if you have enough money.  The money will come from the monsters that you killed.  You can also put some gems in it, which will heighten its power.  The monster will get stronger as you make progress, so you need to upgrade.