Everything in the catalog

Interactive essay on when groups of people judge well and when they herd, with small models to try.

Converts an SVG into G-code for plotters, lasers and CNC machines.

Fast Game of Life simulator using the Hashlife algorithm, with pattern library.

Produces recommended TLS configuration snippets for web servers, databases and mail software.

Open prompt library for ChatGPT, Claude and Gemini that you can browse, copy and share.

Converts PDF files to Markdown inside the browser without uploading them.

Simulates G-code for milling in the browser and shows the cut result.

Live preview for Discord embed and webhook JSON so you can see how a message will render.

Online sheet music editor based on LilyPond with live preview and publishing.

Writes JavaScript for Espruino boards and uploads it over Web Bluetooth or Web Serial.

Web-based collaborative editor for live coding sounds and images with several engines.

Generates and edits coats of arms from heraldic parts, with random or hand-built shields for fantasy factions.

Compiles Sass or SCSS to CSS in the browser.

Markdown editor with live preview that works in the browser as a progressive web app.

Markdown editor for composing WeChat Official Account articles with a formatted preview.

Explainer on how fireflies and other oscillators fall into sync, with a simulation you can adjust.

Comic-style tutorial that teaches spaced repetition and lets you practise it with a flashcard deck.

Browser terminal that installs and runs WASI WebAssembly packages.

Non-destructive image editor with layers, masking and animation that runs in the browser.

Free invoice maker for freelancers and small businesses with PDF export.

Compiles C and C++ to WebAssembly and shows the text format and assembly side by side.

Makes a simple text-based logo and matching favicon from a name, font and colors.

Play Connect 4 against a solver that can score every possible move.

Collection of small calculators for everyday topics, with active calculator packs cached for offline use.