MicroBlocks is based on the GP language: http://gpblocks.org/

You might want to read Mark Guzdial's blog for more on that:

> What makes GP remarkable is that it aims to be a general purpose language. John’s vision for GP is to be the language that students might move to after Scratch, with the highest possible ceilings. Think about GP as Python or Smalltalk in blocks — and even more the latter than the former. From the virtual machine (VM) on which it runs to the class browser, GP feels like a blocks-based form of Smalltalk. Because GP is VM-based, it’s portable — there are versions for Mac, Windows, iOS, and even a JavaScript implementation of the VM so that GP runs in the browser.

– https://computinged.wordpress.com/2016/06/13/introducing-gp-...