Real-life version of 'Harry Potter's Magic Diary': The written words disappear by themselves, and AI still talks to you stroke by stroke on the paper.

According to monitoring by Beating Intelligence, developer Maxime Rivest has open-sourced a project called riddle, which recreates the screenless skeuomorphic interaction of Tom Riddle’s diary from Harry Potter on the reMarkable Paper Pro e-ink tablet. Users write questions on the paper with a stylus; after lifting the pen, the handwriting automatically fades and disappears. Then the large model recognizes the image and streams the content back. The device dynamically writes the reply stroke by stroke in handwriting, and after reading, it fades away again.

To achieve a smooth “air handwriting” animation on the e-ink screen and reduce latency, riddle uses low-level system takeover and software modifications. On the input side, the program bypasses the system’s higher-level input stack and directly reads 4096 levels of stylus raw pressure via evdev. On the output side, a low-level interception shim pauses the tablet’s official UI process, directly takes over the dedicated proprietary e-paper waveform engine libqsgepaper.so, and writes frames directly to video memory. At the same time, the project uses the Zhang-Suen thinning algorithm to extract the skeleton of the Dancing Script font, dissolving the glyph shapes into center paths with a single-pixel width to trace the pen stroke trajectory—thereby perfectly replicating the stroke-by-stroke handwriting dynamic playback animation.

However, riddle has only been tested successfully on specific system versions of the reMarkable Paper Pro. Because it requires root privileges to run and involves taking over drivers, improper operation may damage the device’s system.