My Ordinary Isekai Adventure Turned Into an RTS Base Defense

Garry finds himself in the world of his favorite game, Regicide, but it seems that instead of throwing fireballs and unleashing lightning to accomplish the objective of the game, he will be forced to play base defense. Can he still slay the final boss, a mad emperor, or will he be stuck behind his walls and towers, unable to proceed due to his unfamiliar power?   In the vivid game world that is suddenly very real, he will need to gather all power and allies he can get before the game enters its endgame, apocalyptic stage.  Fast paced, MC's power will come from an RTS base defense game. There are some LitRPG elements