Keen is an upcoming general-purpose programming language.
It's currently in alpha state. There will be breaking changes.

Some interesting features:

• Keen programs can be run directly with no build step, or built to a JAR or JS file.
• Everything is an expression, including if and for. Expressions are nested using indentation.
• The meaning of an expression depends on the expected type.
  The same syntax 1, 2 could be an array, tuple, vector, etc., based on where it is used.
• Everything goes in modules; there are no globally visible declarations.
• Keen is strongly typed, with no subtypes or nulls.
  It does have some safe implicit conversions, but no user-defined ones.
• Global state is restricted. Usually side effects are done through interfaces.
• The type system tracks mutability and prevents sharing non-thread-safe mutable data across threads.
• Specs allow you to call functions provided by the caller's context.
• Contexts provide an alternative for repetitive parameters.

To get started, read the intro.