GTA: Kingdom Rush
The kingdom is under attack, so the king summoned you to defend the castle. You and your men must make sure that none of the enemies reach the castle. The game is played via mouse and the idea here is to the towers to where they would be most effective. There are four kinds of towers that you could use. Each one has its strengths and weaknesses. You can buy some upgrades with the stars that you earn after every level. The game becomes harder as you make some progress, but never fear as you would be unlocking powerful towers as well.