Kingdom Rush

Kingdom Rush is developed by Ironhide Game Studio and published by Armor Games in 2011. It is available online on armor games, iOS, and Android. It is a tower defence game. 

The player has to survive waves of enemies in order to complete a stage. The number of waves may depend on the stage. The player is given a number of lives and gold at the start of the game. The number of lives given to the player depends on the mode the player is playing. Player will be given 20 lives in campaign mode or a single life in heroic challenge mode or iron challenge mode. The lives of the player decrease if an enemy goes past your end of the arena. Weak enemies can only reduce one life per enemy while higher ranked and stronger enemies can reduce more than one life per enemy. Boss enemy may even take 20 lives from the player if it goes past your defence. If the player manages to have one or more lives at the end of the waves, the player clears the stage. Stars will be given depending on the player's performance.

The gold is used to build towers, which will attack the incoming enemies automatically, and upgrade them. There are 4 basic types of towers in Kingdom Rush: Archer Tower (high rate of fire, low damage, targets flying and walking enemies, inflicts physical damage, large attacking damage), Mage Tower (slow rate of fire, high attack damage, targets flying and walking enemies, inflicts magical damage, small attacking range), Barracks Tower (produces soldiers to hold enemies, soldiers inflicts low physical damage, maximum of 3 soldiers per tower at a time, unable to attack flying enemies), and Artillery Tower (inflicts high, splash, physical damages, low rate of fire, intermediate range). The basic towers can be upgraded to 2 different towers each. 

User choose between the 2 bottom most tower upgrades

The enemies possess specific strengths and weakness of their own depending on the type. Some enemies can fly instead of walking on the ground and cannot be targeted by artillery towers and barrack towers. Some enemies have high physical armour which will reduce the physical damage of towers such as archer towers, barrack towers, and artillery towers. Some enemies have high magical armour which reduces the magical damage done by mage towers. Some enemies can move faster than other types of enemies. Aside from physical and defence characteristics, enemies may have special abilities. For example: Spider Matriarch can lay eggs in middle of the path and hatch Spider Hatchlings, thus increasing number of enemies. Trolls have the ability to heal themselves slowly. Troll Chieftains can heal other Trolls near him and increase their physical qualities (attack and speed) and defence (both magic and physical) for a limited time. Necromancers can spawn Skeletons and have ranged attacks. Necromancers will usually place themselves behind the Skeletons they summoned, making them harder to kill.  Enemy types depend on the combination of these attributes. There are no enemy that is invincible. 

The player can control hero as they desire. There can only be one hero at a time. The hero acts like soldiers produced by barrack towers except that they have special skills and are able to level up. Hero is stronger than ordinary soldiers. The player can choose the hero they like in the hero’s room once it is unlocked. 

Sources:

castle games kingdom rush walkthrough

kingdom rush wiki

personal experience