Physics
Damped Oscillation
x = A e^(-ζωt) cos(ω_d t)

A mass on a spring with light damping: the exponential envelope bleeds energy out of the oscillation, integrated live with the library's RK4.
Computed & rendered in pure C# on the frozen OnlyCSharp 1.8 library — animation baked to GIF with the library's own
Gif encoder (no GPU, no ffmpeg, no external packages).