I made this as a rough clone of
https://github.com/iSoron/uhabits, with a goal of having it be cross-platform (it's a PWA so you can use it like a native app on Android phones), and with cloud sync. (The uHabits app lets you export a backup, but doesn't sync habits to the cloud, which has led to me losing habit data in the past.
Would love to hear any feedback!