he idea for the sentry robot originated for the need to have an automatic turret for a school Halloween function's nerf war. The original concept was to just have the turret mounted and fire at anything that breached a proximity IR sensor's threshold. But the idea evolved into something a little more complex. The IR proximity sensor would be mounted on a servo along with the actual gun, and the sensor would pan back and forth searching for targets, and moving the gun and firing accordingly. While selecting a mount for the gun, it was also decided to mount the gun on a mobile platform, allowing the user to reposition the gun remotely, or even incorporate autonomous navigation. Despite the idea for the autonomous sentry arising from a ridiculous scenario, the use of such a robot has a practical purpose, and given a more robust design and an actual, bullet-firing gun, the robot could be used for many military applications