UX Engineer @Microsoft | creator of those easing functions | building next-gen Responsive Easing tools
Brooklyn, NY
Joined October 2008
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I'm building a motion curve editor beyond your wildest fantasies.
I've been head down solving new easing equations for the last 13 months.
I promise nothing less than a quantum leap in easing technology.
Robert Penner retweeted
XState v6 is now in beta 🚀
Reduced API surface area (transitions are just functions), much stronger types, durable execution, new tools (CLI, viz, editor), and more to come.
Built for humans *and* agents 🤝
npm i xstate@beta
stately.ai/blog/2026-11-05-x…
After 10 days of using Bend2, I am thoroughly hooked.
Migrating core TypeScript logic to Bend's functional style, with laws and proofs, feels very satisfying.
A frontier language's limitations are fun though; you get to roll your own solutions.
I worked around Bend's lack of 64-bit math by proving my easing algebra with fractions.
in JavaScript, 0.1 + 0.2 ≠ 0.3. 😵💫
It's actually 0.30000000000000004.
But 1/10 + 2/10 = 3/10. ✅
Because fractions never round, algebra can operate on them exactly.
That lets Bend prove laws with algebra variables ("for all t"), instead of testing samples like unit tests do.
For example, I proved that my Back-in easing:
(s+1)t³ − s·t²
is an exact cubic Bézier, with inner control points:
(1/3, 0)
(2/3, −s/3)
Robert Penner retweeted
Euler's formula (eⁱᶿ = cos θ + i sin θ) is fundamentally a dynamic statement about rotation, growth, and circular motion in the complex plane.
Robert Penner retweeted
I wrote a new article about a liquid effect I implemented 5 years ago. (It's been a while)
Stable Fluids is used in this algorithm, and I explain how I applied it to create the liquid effect in this article.
There are also small interactive demos and you can play with them!
mofu-dev.com/en/blog/fluid-f…
Robert Penner retweeted
I'm on a tear with Bend 2, migrating all kinds of business logic and verifying it.
Synchronous collaboration between Bend and TypeScript feels incredible.
No more modeling/verifying in Lean and porting insights to TS. The laws are live in Bend.
I love leveling up in automated testing.
This year I've climbed up from examples to laws.
A unit test is an example. It's like firing one dot in Battleship.
But prove a law, and you sweep the field in a huge swathe of truth.
Robert Penner retweeted
Made mine with /statechart + Colorfigures, then made them walk around ☕
A metro station whose floors fold, a coffee bean from branch to cup, a slow Saturday on a dice roll, a farm where every animal talks.
Isometric, animated, every bit clickable~
show me the all the cool charts you've made with /statechart! and bugs that you've found using the /create-formal-verification skill
you can install pstack here: github.com/cursor/plugins/tr…
Robert Penner retweeted
Today, we're shipping real-time graphics.
Using Sol 6.1 Ultrafast we can generate custom overlays, diagrams, and even interactive 3D scenes right on a user's screen, no chat.
It's a new visual interface for AI.
Here's me learning about LLMs + hardware.
Demo:
Robert Penner retweeted
Using the right words can drastically improve the results you get from your agents, which is why I built a vocabulary of 244 terms for aiforui.dev.
If a term is used in a lesson, it gets a dotted underline. You can hover to see its definition or click to see a demo.
Robert Penner retweeted
I think it's becoming rather clear that ALL of mathematics will become possible to formalize rather soon. There are deep implications:
1. Mathematics becomes super interactive. Formalizations make it easy to browse, recombine, and build mathematical proofs from components.
2. Each new idea and paper can be checked much faster. The deep part is meaning and explanation. Validation is almost automatic.
3. Optimization and identification of new proofs can be done partially via agents, and humans can contribute much faster with great new ideas. Proofs from the Book are possible at scale.
4. Scientists and people at large can finally use mathematical artifacts as black boxes with trust and confidence. We can commoditize mathematical theorems.
I think the mathematical enterprise also becomes very gamified. We can clearly see each unproven statement as a concrete goal, identify existing tools and directions, and focus quickly on what's missing. And everyone can contribute, with agents or through understanding.
Soon, new languages and new theories will also develop, but the structure will keep growing steadily, with no mistakes and on fundamentally solid foundations. Hilbert's dream is becoming a reality.
One important caveat: mathematics is by no means trivial now! It's just becoming extremely well-structured and laser-focused. I think the jump in capacity, quality, and scale will be massive. I also hope that our understanding of the big picture will remain solid, because there will be a lot to grasp.
Robert Penner retweeted
HBO's @LastWeekTonight has a long track record of citing social science findings without the appropriate context, massaging them to support whatever point @iamjohnoliver is trying to make.