Snap! has the full power of Scheme (first class functions, user defined blocks, recursion, closures, continuations, JavaScript integration, etc), with a visual block syntax and playful graphical environment with turtle graphics like Scratch.

The following post is a couple years old, but maybe somebody can provide some updates and recent info!

Edit: I should have RTFA first, which is totally up to date, just published in 2020, from the turtle's mouth:

https://escholarship.org/uc/item/1623m1p3

>Brian Harvey’s Personal Narrative on Snap!: Scheme Disguised as Scratch

>In 2009, the University of California, Berkeley, was one of several universities developing a new kind of introductory computer science course, meant for non-CS majors, to include aspects of the social implications of computing along with the programming content. Scratch wasn’t quite expressive enough to support such a course (it lacked the ability to write recursive functions), soProf. Daniel Garcia and I thought “What’s the smallest change we could make to Scratch to make it usable in our course?” After 20 years teachingStructure and Interpretation of Computer Programs[Abelson et al.1984], the best computer science text ever written, I knew that the answer to “what’s the smallest change” is generally “add lambda.” I joined forces with German programmer Jens Mönig, who had developed BYOB (Build Your Own Blocks), an extension to Scratch with custom (user-defined) blocks, including reporters and predicates. [...]

https://news.ycombinator.com/item?id=17594403

DonHopkins on July 23, 2018 | parent | favorite | on: Ask HN: Best Lego Mindstorms alternative for fun p...

One of the coolest ways to learn programming I've ever seen is the Snap! visual programming language, which is written in JavaScript and runs in the browser.
https://snap.berkeley.edu

It's the culmination of years of work by Brian Harvey and Jens Mönig and other Smalltalk and education experts. It benefits from their experience and expert understanding about constructionist education, Smalltalk, Scratch, E-Toys, Lisp, Logo, Star Logo, and many other excellent systems.

Snap! takes the best ideas, then freshly and coherently synthesizes them into a visual programming language that kids can use, but is also satisfying to professional programmers, with all the power of Scheme (lexical closures, special forms, macros, continuations, user defined functions and control structures), but deeply integrating and leveraging the web browser and the internet (JavaScript primitives, everything is a first class object, dynamically loaded extensions, etc).

Y Combinator demo:

https://i.imgur.com/cOq8tvR.png

https://snap.berkeley.edu/snapsource/snap.html#present:Usern...

Here's an excellent mind-blowing example by Ken Kahn of what's possible: teaching kids AI programming by integrating Snap! with existing JavaScript libraries and cloud services like AI, machine learning, speech synthesis and recognition, Arduino programming, etc:

AI extensions of Snap! for the eCraft2Learn project

https://ecraft2learn.github.io/ai/

>The eCraft2Learn project is developing a set of extensions to the Snap! programming language to enable children (and non-expert programmers) to build AI programs. You can use all the AI blocks after importing this file into Snap! or Snap4Arduino. Or you can see examples of using these blocks inside this Snap! project.

https://github.com/ecraft2learn/ai

http://lntrg.education.ox.ac.uk/presentation-of-ai-cloud-ser...

Use devices with Snap!:

Orbotix Sphero guide by Connor Hudson and Dan Garcia:

https://docs.google.com/document/d/11wR53OTnofRtTtxZCmxnCUjI...

Lego NXT package by Connor Hudson:

https://github.com/technoboy10/snap-nxt

Nintendo Wiimote package by Connor Hudson:

https://github.com/technoboy10/wiisnap

Finch and Hummingbird robots package by Tom Lauwers:

https://www.hummingbirdkit.com/learning/snap-programming/

Parallax S2 robot package by Connor Hudson:

https://github.com/blockext/s2

LEAP Motion by Connor Hudson:

https://github.com/technoboy10/snapmotion

Speech synthesis by Connor Hudson:

https://github.com/technoboy10/snap2speech

Arduino package by Alan Yorinks:

https://github.com/MrYsLab/s2a_fm

Arduino package by Bernat Romagosa/Citilab:

http://snap4arduino.rocks/

Fischertechnik ROBOTICS TXT Controller by Richard Kunze:

https://github.com/rkunze/ft-robo-snap

Snap! for Raspberry Pi by rasplay.org:

http://downloads.rasplay.org/pisnap/

More Snap! extensions for CS education:

snap-apps.org provides Edgy for graphs, Cellular for multi-agent simulation, and more.

http://snap-apps.org/

http://www.snap-apps.org/edgy.html

http://www.flipt.org/#cellular

Netsblox for multiplayer networking.

https://netsblox.org/