If you're a fan of @worrydream's Inventing on Principle, check out Seymour, a live programming environment I made with @sakekasi.

RT @geoffreylitt: New longform @inkandswitch essay! 📜. Malleable Software.by me, Josh Horowitz, @pvh and Todd Matthews. .

RT @geoffreylitt: what if you could model a problem in a spreadsheet, and then instantly start applying powerful *filters* to explore your….

Curious to learn more? We're publishing a series of notes about our experiments. Our first note introduces how amb values work and why they improve on existing spreadsheets:

What if a spreadsheet cell could hold multiple values at the same time?. That's the idea behind Ambsheets, a project I've been working on w/ @geoffreylitt at @inkandswitch. It's a new spreadsheet that makes it easier for you to explore many possibilities simultaneously. 1/2

I spent about 45 minutes making this. After I showed it to Alan, he gave me an internship at VPRI, working on the STEPS project. A couple of months later, he would be co-advising my Ph.D. Best ROI *ever* on writing a computer program. 3/3.

The hero of this story is Etoys' "color sees" tile. When the wire's red sensor sees the color yellow, the wire turns yellow. Otherwise, it turns black. You can make AND, OR, NOT gates the same way -- it's nothing that a 5th-grader would have trouble making on their own. 2/3.

Logic Game, 2005. I made this logic circuit simulator to learn Etoys, Alan Kay & co.'s programming language for kids. I represented the state of the wires and logic gates with their "costumes" -- there is no hidden state. This makes the behavior of the circuits visible. 1/3

Sketchpad running on the iPad!. (This is my plug for the @inkandswitch wrapper, check it out at

RT @geoffreylitt: We're now sending out monthly email newsletters at @inkandswitch -- sign up at the bottom of the lab website if you wanna….

Fellow technologists: next time you use 'incredibly' in a sentence, consider omitting it altogether. You'll be *incredibly* glad you did.

Constraint-Based Spreadsheet, 2014. An attempt to make spreadsheets more powerful and user-friendly by replacing one-way formulas with multi-way constraints. Check out the source code (@_ohmjs inside!) and play with the live demo at

To play with a live demo and see the source code, go to

In this prototype, I also experimented with a purely textual way to bind the values of different number "tokens" to each other. All you had to do was type a variable name immediately after the number. Numbers with the same name would have the same value.

But if scrubbing a number is like turning a crank, what's the equivalent of leverage / mechanical advantage? Can we get even more useful information from this interaction? I have several ideas here, but I'll leave it as an exercise for the reader :).

This is a manual process: all of the information in the graph comes from the user's interaction. That feels nice — it's like you're turning a crank and getting useful information in return.

So I added graphing as a fleeting mode: if you hold down "alt" while you scrub, the system remembers all of the input-output pairs you've seen and graphs them. This lets you see the relationship between the "variable" you're scrubbing and the result more easily.

I started by writing my own scrubbing calculator, which you see in this video. When the user scrubs a number, the result changes. This is helpful, but you're looking at a possibly complex relationship through a peephole, one input-output pair at a time. We can do better.

Graphing Scrubbing Calculator, 2013. I was inspired by @worrydream's "scrubbing calculator" to explore UIs in which some of the text you type gets widget-like superpowers automatically.

Sketchpad: two-point perspective

Soccer ball launcher prototype, 2023. MicroPython / Raspberry Pi Pico,.dual motor controller, and.a couple of DC motors.