The object of the game is to prevent the hordes of monsters from getting to the castle by building element towers near the path.
You can choose from a number of different elements to build towers from.
The monsters will spawn every 20 seconds.
Their health will be multiplied by 1.25 with every wave.
If your towers fail to kill the monsters, and they do get the castle, a civilian of your castle will die.
When all your civilians die, the game will be over.