New architecture! The v3 of Mercury is based on Tornado server, and is using Jupyter Lab frontend to serve widgets in the same way as in Jupyter notebooks. Thanks to this we get greater flexibility in what we can do with app. We use ipywidgets and anywidgets packages to create easy to use and looking-great collection of widgets. The v3 version contains Mercury extension for Jupyter Lab and MLJAR Studio which allows you to preview app during development.
I hope you will be able to create amazing apps with Mercury! ❤️