FOLD file format for origami models, crease patterns, etc.
Fast math typesetting for the web.
Tool for drawing diagrams on a grid, combining grids of SVGs into a big SVG figure
Customize replacements in markdown-it typographer
Create custom SMTP servers on Node.JS version 4
Send e-mail with Node.JS version 4
Custom level design for Recursed via spreadsheets
Synchronize form state (and other state) with URL