Kingdom Rush can be played for free on sites like ArmorGames.com and Kongregate. Kingdom Rush is also available on Steam at a price of $9.99.
Kingdom Rush is a fantasy-based tower defense game, where players fend off enemies through strategically placing and upgrading turrets and soldiers to fight waves of approaching enemies. Each tower can also be customized with different types of units and abilities, allowing the player to formulate the optimal strategy to clear each level. The game is available on PC, Android and Apple devices.
Two expansions are also available in the Android and Apple marketplaces: Kingdom Rush Frontiers and Kingdom Rush Origins. However, only the original, Flash-based Kingdom Rush can be played for free.