You need to protect your tower from the pirates. They are hiding in the buildings and surrounding areas waiting for the perfect time to attack. You need to find the pirates in each level and destroy them. Once you clear out all the pirates from one level, you will unlock the next level. Each level gets harder as you venture into new territories. Wood structures are easiest to knock down, followed by stone and then steel. Looking at each level and figuring out an attack strategy is key to winning. Most levels have coins which you can collect by shooting them. You can use the coins to buy extra cannonballs to continue playing a level. In later levels, there are explosive cannonballs, which you will need to use wisely to complete them.