A parallel to “earliest game” topic elsewhere in this category:
Not exactly a game, but it could be. In the 2nd grade, following the plans in a book, I (with grandfatherly help–he really wanted me to get in on this new-fangled “computer” thing that he heard was the future) made my first computational device, “programmed” by routing bell wire pieces according to a diagram. A cigar box enclosure, brass tacks for the terminals, and flash light bulbs for output, cut plywood “knobs” for input. It accepted two 2-bit inputs (numbers 1 through 4) from the two plywood rotors, and the output was one of seven bulbs (numbered 2 through 8) lit showing the sum of the inputs. A two bit adder!
What it did for me was remove the “magic inscrutability” of computers…I could easily imagine, multiply this cigar box by a few million, and you get the IBM System 360 (a big deal back in those days).
My first “real” computer program was something like:
10 PRINT "HELLO"
20 GOTO 10
in Applesoft Basic on the Apple II+ in the 8th grade. That was when I learned you could program a computer without hard-wiring it.