Time for some warm-and-fuzzies! What happy memories do you have from your early days of getting into computers/programming, whenever those early days happened to be?

When I was in middle school, I read an article in Discover Magazine about "artificial life" — computer simulations of biological systems. This sent me off on the path of trying to make a simulation of bugs that ran around and ate each other. My tool of choice was PowerBASIC, which was like QBasic except that it could compile to .EXE files. I decided there would be animals that could move, and plants that could also move. To implement a rule like "when the animal is near the plant, it will chase the plant," I needed to compute distances between points given their x- and y-coordinates. I knew the Pythagorean theorem, and I realized that the line between the plant and the animal is the hypotenuse of a right triangle. Tada: I had invented the distance formula!