...Its functionality may include showing balance, last transaction, QR codes, or other custom info on the e-ink screen, and interfacing with smartphones or readers via NFC. Because it uses e-ink, the card can display static content with minimal power drain, making it practical for real-world card use. The repository includes board design files, firmware, and supporting software for customizing what the card shows. For hardware hackers and smart-card enthusiasts, it’s a fascinating hybrid of microcontroller, low-power display, and NFC tech in a familiar credit-card size.