Cat Heroes - Merge Defense is a free iPhone game developed by DUK KEUN KIM. This defense game puts you in control of a team of cats with different abilities, tasked with preventing enemies from invading. The objective is to merge identical cats with the same levels to create higher phase cats that are stronger. By combining heroes and building powerful decks, you can effectively defend the planet from enemies.

The gameplay is simple and addictive. You start by summoning and merging the cats, and once they are batched on the field, the battle starts automatically. To progress, you need to upgrade your cats and items, and develop strategies that suit the enemy and boss.

Overall, Cat Heroes - Merge Defense offers an entertaining defense game experience with its unique merging mechanic and strategic gameplay. If you enjoy defense games and love cats, this game is worth a try.