In this game you go through ranks,from private to general, in the effort of defending most eastern part of Ottoman empire in early 19th century. To do this in your disposal is nine types of towers,within three category and range option. Every tower have max of three tier, to be upgraded, and each tier have three slot that can be fill in with mercenaries. Mercenaries have five ranks and three specialization, witch each affect some of towers properties. In addition of that there are numbers of passive and active abilities, that can be use in game.
To unlock your slots you must upgrade your rank, be winning and earning stars. More stars, faster you will be gain new rank, and better reward stats will be earned (stats are depending both of earned stars and your current rank). You can (re)play each level how many times you wish, earning stars and rewards each time.