Plinth is an object-oriented language designed to be fairly terse, with very good support for safety and binary compatibility. It contains some unusual features, such as variables not being nullable by default, along with many more familiar ones, such as properties. It has a very expressive type system, which provides for strong immutability as well as functions, tuples, and the ability to make any type nullable.
This site currently only covers some of the basics, but it aims to eventually document all of Plinth’s features.
Plinth is open source, and is hosted on GitHub at: https://github.com/abryant/Plinth