Differential equations,
the way you can see them.

An interactive, visual playground — slope fields to chaos.

Every idea starts from something real — a cooling cup of coffee, a child on a swing, a switch that snaps — and is anchored to a picture you can play with. Drag the sliders, watch the animations, and edit and run the code, all in your browser. No install, no prerequisites beyond first-year calculus.

Runs in your browser — nothing to install No prerequisites — terms are earned, not assumed Free & open source
Live: a pendulum's phase flow — every dot is a starting state finding its fate.

Read it now

Chapters available today. Each reads top-to-bottom; expand any cell to edit and re-run its code right in the page.

Where it's going

The full arc — a standard undergraduate differential-equations course, built one interactive chapter at a time. available means you can read it today; draft means it's readable but still being written.

Part II · Higher-order & transforms · oscillation, resonance, Laplace

Part III · Qualitative dynamics · what the flow does without solving it

  • Fixed points & stability
  • Bifurcations in 1-D
  • Flows on the circle
  • Linear 2-D systems
  • Nonlinear phase portraits
  • Limit cycles
  • Bifurcations in 2-D

Part IV · Partial differential equations · variation in space and time

  • Intro to PDEs
  • Heat equation
  • Wave equation
  • Fourier series

Part V · Chaos · sensitive dependence, strange attractors

  • The Lorenz attractor
  • One-dimensional maps
  • Fractals

What makes it different

Not a PDF with a few plots bolted on.

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Stories first

Each chapter opens on a concrete phenomenon and builds the math out of it — the equation is derived, never dropped from the sky.

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Everything moves

Sliders, 60-fps animations, draggable masses, an audible resonance curve. The intuition is something you do, not something you read.

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Real, runnable code

Every figure is generated by Python you can edit and re-run in the browser — and an open playground in each chapter to try your own.

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Honest derivations

Hand-built animations walk the hard algebra step by step, so the "trust me" moments are kept to a minimum.

An optional AI tutor rides along in every chapter for free-form questions. It's bring-your-own-key (Anthropic): your key stays in your browser and is sent only to Anthropic, never to this site. Every chapter is complete without it.