When I was REALLY young, like 4 years old, I pried apart a 5-1/4 inch floppy disk and drew a game concept in pen on the surface of the disk. Needless to say this didn't work, but surprisingly the disk still allowed me to read and write data to it!
You remind me why kids can be awesome.
My first games were Choose-Your-Own-Adventure games "programmed" in Hyperstudio, this early Apple equivalent to Powerpoint, around 4th or 5th grade.
OH man, there were *dozens* of those at my grade school. Hypercard was awesome.
Wasn't the first Myst made entirely in Hypercard?
Also, my first mostly-completed game is still the only one in my signature, Minus. the first serious attempt at a game was a Game Maker shmup with colored squares. I made some things with it that for me nowadays are trivial but back then made me feel like a programming genius.