There is an emulator on the web, so develop something simple and the order one. I wanted to buy ten watches so Bangle.js was not an option, but if you just want something programmable I do recommend it.

https://www.espruino.com/ide/?emulator https://www.espruino.com/Bangle.js+First+App

Their "app store" is online [0] and you can actually review the source code for all of the apps on it by clicking the github icon on each entry, here's one for example [1]

[0] https://banglejs.com/apps/?c=game [1] https://github.com/espruino/BangleApps/tree/master/apps/blac...