This is a classic Tower Defence game. Defend your base (represented by the banner) from monsters that appear on the road by building turrets. There are different monsters with different characteristics, also some boss monsters. Each level is unlocked by finishing previous one. There are different turrets that can be upgraded by clicking on them. To build the turret click on the image of it on the right, then place it on the green tile on the map. You earn gold by killing monsters, use it to build more turrets. When some number of enemies reach the base the level is lost. Buy Upgrades between levels to boost your stats. Upgrades use stars as currency. Stars are obtained by finishing levels. You can try Hard difficulty to earn more stars and make the game more challenging, or Easy if levels are too difficult.