Use the mouse to target enemies. Click on the left mouse button to fire your weapon. There is an icon below that appears on the left side of the screen every time you switch weapons. A silhouette will be shown inside of it after you buy a weapon. The red bar on the right of it indicates the remaining ammo for that weapon. The ammo indicator is located on the top left of the screen and shows your selected weapon's ammo. Your inventory shows your current item. There are four types of items. The first two are bombs and mines. When one of these is selected and you press Spacebar the bomb or mine will from your crosshair to the ground. The last two items in your inventory are turrets. The 1st is the ground mounted turret. If you select this item, a transparent turret will be shown on the ground and will follow the mouse position. If you move the mouse to the right of the screen, the turret will point to the right and visa versa. Once you picked a spot press the Spacebar to plant the turret. The castle-mounted turrets behave the same. The only difference is that you can place the turret along the wall of the castle. Fore performance purposes you can only have a maximum of four turrets at a time. After a turret takes enough damage or runs out of ammo it will self destruct. Also, you can't place more than six mines at a time. Wait for a few to explode and then keep adding. Your objective is to defend the castle. Your mines and turrets don't damage the castle, but your guns does. The castle can be repaired and even strengthened in the weapon shop. Use the coins that you collect from the enemies to buy new weapons or repair the castle. Place the mouse over an item in the weapon shop to see a description. Click on that item to buy it.