Koopatrol: Castle Guard

Your king has kidnapped princess Peach, and the Mushroom Kingdom is sending its forces to try and get her back. You, as the loyal subject of King Bowser, have to protect the castle from the intruders. 

Depending on screen width, issues with the tutorial may arise; do not play in full screen mode if you're doing the tutorial. If you download the game, you'll have access to a level builder and high scores.