A replica of Citizen Quartz watch based on Harel's paper introducing statecharts (andyjakubowski.github.io)

If you're fond of state machines as an abstraction for system design, I highly recommend reading the Harel statechart paper. It's well-written and understandable. And, it's truly a useful extension of the type of state machine diagrams software engineers typically produce.

This is very cool, but why does the battery die so quickly?

Simply awesome. One thing I would suggest cleaning up is batteryPercentage which shows something ugly like 98.1000000000006 at least for me.

Delightful!

I always wanted to implement a graphical statechart editor specified in statecharts, or even implemented in executable statecharts.

Very cool! I created something similar for Casio F-91W. It also uses XState. The benefit of specifying a machine in XState, is that one can embed Stately editor to visualize the states and their transitions.

https://github.com/dundalek/casio-f91w-fsm

Beautiful! I love the clean design of the page, too. I went through a period of obsession with the Harel paper, and your page is a nice summary of some of the key points!

Anyone else seeing how fast they can start/stop the stopwatch? I got .08 once but mostly .10-.12.