A polyrhythm is two or more steady pulses occurring at different rates. I made this browser-based polyrhythm metronome with automation capabilities. I wrote it in javascript using the WebAudioAPI. With the automation feature one can work on transitions or automate whether or not to have the app play the shared subdivision of the two steady pulses.
I leaned heavily on Chris Wilson's 'A Tale of Two Clocks' https://web.dev/articles/audio-scheduling and had a light bulb moment after studying Simple Metronome by Grant James https://grantjam.es/
The metronome is live here https://doughirlinger.com/polyrhythmic-metronome/