The Iron Gate is under attack! As Gatekeeper, your duty is to fend off the enemy soldiers trying to storm this impenetrable citadel. The king has sent all of the army, but all were slain except for you. And you must act before you end up just like every other soldier. Use the arrow keys or WASD to run, and point your sword with your mouse pointer. Click or press space to swing your blade. Now, go, before the gate is taken! (Also click the flag twice after every game.)
Credit to @LoudHeadphones for the in game music, and to @Sirmonke and @ZappyBarbecue10 for the game over music.