In 1972, this must have felt like stepping into the future. TVs had only ever been passive, and suddenly the screen could respond. Families were seeing their living room sets turn into game machines, with paddles controlling little glowing squares.

Now, the overlays look wild. Plastic sheets taped to the glass to turn dots into tennis courts or haunted houses. It’s clumsy. Also brilliant—an early hack to add color and imagination to an otherwise bare signal. You had to supply the magic yourself, which makes it all the more fascinating today.

And the way Magnavox pitched it. What are you going to do when your kids are snowed in? It was sold like a family appliance. Little did they know that this would be revolutionary.