Mario and Friends Tower Defense involves you setting up defensive units throughout the tunnels that lead to the all important Castle. If Bowser's evil forces of Goombas, Shy Guys, and other baddies are allowed to reach the Castle, they will steal your Flower Power. And if your Flower Power reaches 0, you lose. To prevent this, you must strategically place Mario and his friends in the Rocky Zones in the tunnels to attack the incoming invasion of bad guys. Placing units on corners works the best since they'll essentially have two chances to hit the invaders. As you progress, you'll earn coins that can be used to buy & research new units.