Currently re-implementing the Focus Sessions feature of the built in Windows clock app. I had been using the Windows version as a quick way to track time spent on a learning goal but found it buggy and lacking some features I wanted (like a pause button!) so I'm rewriting it as an Electron app. It's giving me a chance to write some plain JS for once and I've set a challenge of importing as few front-end libraries as possible (so far only react and immer). I'm excited that I have it at the point where I can dogfood it for tracking the time I spend on developing it.
