CircuitJS1 is an open-source electronic circuit simulator that runs in the browser — Paul Falstad's tool, with the source at github.com/pfalstad/circuitjs1.
esaruoho is a sustained contributor — see Contributions to circuitjs1 for the full PR and commit log.
Work spans the simulator's physics models (MOSFET channel-length modulation λ, BJT junction capacitance CJE/CJC and transit time TF/TR, MOSFET gate capacitance Cgs/Cgd, diode parasitics, saturable core for inductors and transformers, lossy RLGC transmission line, Jiles-Atherton B-H hysteresis), measurement and display (oscilloscope trigger mode, peak-to-peak voltage, RMS for non-sine waveforms, FFT in dB, CSV export, logarithmic sliders), workflow (keyboard-shortcut switches, configurable propagation delay on logic gates, configurable rise/fall on square/pulse waves, slider step increments, save/load filename tracking), and platform plumbing (Gradle wrapper for reproducible builds, GitHub Actions CI, .editorconfig, macOS Electron Cmd+C/V/X/A menu fix, test.sh for quick local build).
The simulator is used for analysing and prototyping schematics — including circuits relevant to the free-energy / unconventional-energy research archived under merlib.