Letter shapes
The traceable letters and numbers are drawn by hand for Penroo as single-stroke paths — they are not a licensed font, so we can control stroke order and direction exactly.
Typefaces
Interface and worksheet title text uses Andika and Fredoka, both released under the SIL Open Font License and used via Google Fonts.
Built in-house
The QR codes and the printable PDFs are generated entirely in your browser by code written for Penroo, with no third-party QR or PDF library.