I used AI to recreate Tom Riddle's magical diary from Harry Potter.

Developer MaximeRivest created the open-source project riddle, turning the reMarkable Paper Pro e-paper tablet into a magical diary that "eats ink" and allows handwritten replies, inspired by Tom Riddle's diary from Harry Potter.
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(Background: AI Renaissance? E-paper Notebooks Defy Trends to Become High-End Workplace Tools)

The magic happens when the ink disappears! Recently, a developer named MaximeRivest used AI to create a delightful user experience: after writing on the e-paper with a stylus, the ink gradually fades as if being eaten, followed by a response appearing like in the Harry Potter novels.

A Diary That Thinks

This open-source project is called riddle, and the author nicknames it "Tom Riddle's diary," inspired by the magical diary from Harry Potter that thinks and responds.

Currently, it only supports the reMarkable Paper Pro (an e-paper tablet designed specifically for handwritten notes). The usage logic is simple: write, pause, wait. After pausing for about 2.8 seconds, the ink gradually fades from the page, the screen "thinks" for a moment, and then replies are written back page by page using the Dancing Script handwriting font, making it look like someone is writing a reply right before your eyes.

I love it when technology feels like magic. pic.twitter.com/7wbjyhyL8D

— Maxime Rivest 🧙‍♂️🦙🐧 (@MaximeRivest) July 4, 2026

The Soul Behind This Diary

This diary can generate human-like text thanks to its AI backend called oracle. In the developer's words, it's "the soul of the diary." riddle's architecture is divided into three layers: the core written in Rust handles pen input and ink animation synthesis, the C/C++ quill directly controls the e-paper's display engine, bypassing the usual UI intermediate layers to reduce latency, and the "thinking" part is handled by oracle.

It defaults to the OpenAI-compatible API. Simply put, as long as a service follows OpenAI's /chat/completions format—whether it's OpenAI official, OpenRouter, Groq, or even a self-hosted local server—it can connect to riddle by changing a few environment variables to switch backends. Another mode runs locally for even lower latency.

Turning the pen over erases, drawing a question mark brings up instructions, pressing all five fingers simultaneously exits the program... The entire project is open-sourced on GitHub under the MIT license.

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