The yellow '1st & Ten' line seen in American football broadcasts was first introduced by Sportvision in September 1998 during an ESPN game between the Bengals and Ravens. This 'augmented reality' feat was incredibly difficult to achieve at the time. It required a 3D model of the field, specialized sensors on the cameras to track pan, tilt, and zoom, and a computer system that could distinguish between the green grass (where the line should be drawn) and the players' uniforms (which should appear 'over' the line). The system had to render the line in real-time, 30 times per second, to ensure it didn't flicker or lag as the camera moved. Today, this technology is standard across almost all televised sports, but at the time, it was considered a miracle of engineering that fundamentally changed how viewers understood the flow of the game.