In this game there will be a castle and a road leading to the
castle.
Enemies will pass through the roads to attack the castle. You lost
the game if the castle is destroyed. You need to buy cannons to
shoot the enemies to stop them from attacking the castle. When
you destroy an enemy, you will get extra money to buy more cannons.
When the game progresses, there will be more and more enemies and
they will become stronger and stronger. There are a total of 10 levels.
