Your kingdom's enemies have tried catapults, spies, clever negotiations, that rabbit from the Cave Of Caerbannog, and every type of siege imaginable, but they simply can't capture your king. So they take the next logical step and attack your castle with a squadron of hot-air balloons. To defend your king, you take a similarly logical step and have him run back and forth across the courtyard while two guys run across a bridge with a crossbow, sworn to defend him to the death. Or until he's taken off the screen three times. Just like in real medieval times, your crossbow shoots laser bolts, and the balloons can move around without regard to the laws of physics, thermodynamics, or gravity.
Gameplay: If a balloon manages to evade your remarkably thin defenses, it will pick up your king and head for the sky. You can pop the balloon by aiming right between the king's legs. If you succeed, he'll float safely back to the courtyard on a precious little umbrella.