Everything in the catalog

MIDI utility for learning piano scales, chords and more using a connected MIDI keyboard.

Generates color scales whose steps meet target contrast ratios for design systems.

Shows contrast scores for every combination in a set of colors.

No-code chart builder that also produces a Chart.js image URL, no login needed.

Puzzle game that teaches functional programming ideas by composing functions to transform cubes.

Add images, signatures and text to a PDF with everything done inside the browser.

Picks and converts colors in OKLCH and warns when they fall outside a display gamut.

Scans QR codes in the browser using your webcam and shows the decoded content.

Simple visual editor for building tikz-cd commutative diagrams and copying the LaTeX.

Open-source web chat front end that works with several AI providers using keys you supply.

Web calculator with user-defined variables and functions, complex numbers, derivatives and integrals.

Free browser-based DAW with a piano roll, sample slicer and synthesizer for composing music.

Runs Dart and Flutter snippets in the browser with a console and a live preview pane.

Scientific calculator language that tracks physical dimensions and units in every calculation.

Simple daily habit tracker without goals, with a public demo.

ASCII sketching app for laying out boxes, lines and labels as monospaced text drawings.

Records the screen into a GIF in the browser, with frame trimming before export.

Turns an uploaded photo into pixel art with adjustable block size and palette.

Free API and web page for generating memes from templates through URLs.

Visual sandbox that draws what git commit, branch, merge and rebase do to the history graph.

Sketch feedback loops with nodes and arrows, then run them to see how a small system behaves over time.

Draw walls on a grid and watch Dijkstra, A* and other search algorithms find a route.

Entity-relationship diagram editor with SQL DDL import and export.

Shows how OpenAI-style tokenizers split text or chat messages into tokens and counts them.