When I was a kid in the 1970's games came in a credit card sized form factor. Pacman, donkey Kong, (MAME types of games). We all had a bunch of these games with us in our bags. Each device could play one specific game.
I remember the orange coloured casing for the donkey kong game we had in the house. It was my mothers, and I eventually grew up with the original Game Boy. But it was my first game device and I played it religiously.
Here is how it looked like. Donkey Kong has dual screens. Most other games only one.
https://upload.wikimedia.org/wikipedia/commons/thumb/d/d9/Ni...