The Pendulum That Taught Me to Code
A double pendulum, a Turkish physics forum, and the first loop I ever wrote.
The first program I ever finished was a double pendulum, written badly, for no one. A forum post claimed its motion could not be predicted, and I took it personally.
I did not know what a numerical integrator was. I invented a terrible one, step by step, the way you reinvent arithmetic when nobody tells you it has a name. The pendulum gained energy from nothing and swung itself to infinity, and fixing that took me three weeks of evenings.
Nobody taught me the loop. The pendulum did — by falling wrong ten thousand times.
Somewhere in those three weeks the thing I was learning quietly changed. It stopped being about the pendulum and became about the machine: state, steps, error, the discipline of making a wrong thing slightly less wrong every run.
Every simulation I have written since is that same program with better manners. The playground on this site exists because of a forum thread I can no longer find, and a pendulum that refused to behave.