Blake's Binder
Blake's Binder is an interactive math textbook that I write and build myself. It runs from ISEE test prep through precalculus, calculus, and linear algebra, up to graduate courses in abstract algebra, topology, measure theory, and number theory, plus a shelf of research write-ups. Every picture on the site is drawn live in your browser, so you can drag it, change it, and watch the math move.
There's still a lot to build, and new pages keep going up. This page is the tour: who I am, what's in the Binder, and how to make it read the way you like.
About the Author
That's the face of someone who just spotted a sign error on the whiteboard.
I'm Josh Blake Flynn II, and everyone calls me Blake. I'm a Ph.D. student in mathematics at the University of Houston, where I work in number theory, mostly Diophantine approximation: how well irrational numbers can be approximated by fractions, and what the geometry of lattices has to say about it.
I teach Precalculus at UH as Instructor of Record, and I tutor remotely with MathTutorsATX. Before that I led Calculus I–III labs as a graduate teaching assistant, ran the study lounge as Lead Tutor at General Academic, taught at Mathnasium, and substitute taught in Katy ISD. I came to math through a B.S. in Mathematics and a B.B.A. in Accounting, both from UH.
My first paper, A Geometric Proof of Peck's Theorem, is joint work with Kavita Dhanda and Alan Haynes. In 1961 Peck proved a sharp result about approximating a whole basis of a number field by fractions with one common denominator, and her proof is famously hard to read. We show the entire theorem falls out of a single application of Minkowski's convex body theorem, in the lattice of logarithms of units. The same picture, bent a little, gives denominators in arithmetic progressions and new progress on a conjecture Peck left behind. The link goes to the paper rebuilt with moving figures; the preprint itself is on the arXiv as arXiv:2609.29469.
Why build a textbook? Because the moment a student gets an idea is almost always a picture, and a page can't move. Here every graph is something you can grab, every practice question can be regenerated as many times as you like, and the wrong answers are the mistakes real students make, so getting one wrong tells you something.
Research · LinkedIn · Email me
What's in the Binder
The menu across the top is split the way a school is: test prep, the core courses, and an Advanced button that opens a second row of graduate courses. Each menu is drawn as a piece of its own subject's math, so open a few just to look.
- Test Prep is a treasure map. Eleven ISEE sections, starting at Section 0, build on each other in order, and the Test Builder writes you a full-length, timed ISEE Quantitative Reasoning or Mathematics Achievement section on demand, with no two the same.
- Pre-Calculus and Calculus: functions, the unit circle, limits, and on up.
- Linear Algebra, computation first, starting from vector spaces. It can be read in two ways (more on that below).
- Advanced: proof-based courses in Abstract Algebra, Topology, Measure Theory, and Number Theory, plus a growing corner on Rubik's Cubes (I'm a speedcuber).
- Research: papers and talks, mine and ones I've been reading, rewritten as pages with looping animations, live figures, and widgets.
The whole site uses one notation, and the Notation page lists every symbol. Glossary words are underlined the first time they show up on a page: hover one to see its definition without leaving where you are.
How a Page Reads
Pages read like a comic book. The commentary is written the way I'd explain things sitting next to you, and the important pieces live in panels, each with its own color.
Red panels say exactly what a word means. When a later page uses the word, it links back here.
Blue panels hold the results. On proof pages the proof sits inside the panel behind a "Show proof" button, so you can try it first.
Purple panels work a problem.
The solution comes after the dashed line, so you can cover it up.
Green speech bubbles are the traps and shortcuts a tutor would point out out loud.
Thought bubbles call back to an earlier page or peek ahead to a later one. On a wide screen they float out into the margins.
Between the panels are the widgets, the part of the Binder I care about most. Some are things to play with, some set you missions, some animate a whole argument on a loop. A small orange ping shows you where to touch the first time; the round button in a widget's corner resets it.
Practice comes right where an idea is taught. Every question has a Choices / Type it switch for multiple choice or free response, and three buttons: Easier version, Another version, and Harder version. Behind them are more than 1,300 question generators, most with five difficulty levels, so you can keep practicing until it's boring. Every page ends with a Spicy Bonus 🌶, a harder problem that ties the whole page together.
Make It Yours: Settings
The Settings button at the top right of every page changes how the whole site reads, and it remembers your choices.
- Code Mode turns the comic book into a computer terminal: dark, phosphor green, monospace, with the five colors glowing like neon and the doodles turned into laptop stickers.
- Handwriting Font switches between the handwritten look and a plain, rounded font. Code Font does the same in Code Mode.
- Comic Boxes hides any kind of panel: just the definitions, no examples, no thought bubbles. Try it now: turn off Pro Tips and watch the green bubble above disappear.
- Page Parts strips a page down further: hide the commentary to get a study sheet of definitions and theorems, or hide the proofs, the widgets, or the practice.
- Graph Elements turns grid lines, axes, tick marks, and labels on and off in every graph.
Linear Algebra has two settings of its own, as stickers on its menu. n × n | 3 × 3 picks the telling: the usual course for any dimension, or the same course retold in dimension 3 for a high school reader, with picture proofs in place of formal ones. ℝ | 𝔽 shows or hides notes on how each idea works over an arbitrary field.
How It's Built
Plain HTML, CSS, and JavaScript, with no frameworks and no build step. Every graph, widget, and menu picture is drawn by hand with D3.js, and the math is typeset by MathJax. The question generators are stress-tested by script, thousands of runs each, to make sure every question has exactly one right answer, friendly numbers, and wrong answers that come from real mistakes.