Real-Life "Harry Potter Magic Diary": The written words will disappear on their own, and the AI will interact with you on the paper stroke by stroke

According to Dynamic Insight monitoring, developer Maxime Rivest has open-sourced a project named riddle, which recreated Tom Riddle's diary from Harry Potter with screenless analog interaction on the reMarkable Paper Pro e-ink tablet. Users can use a stylus to write a question on the paper, and once the stylus is lifted, the handwriting will automatically fade away. Subsequently, a large model recognizes the image and streams back the content, and the device dynamically writes out the reply in handwriting, which then fades away after reading.

To achieve smooth "air writing" animation on the e-ink screen and reduce latency, riddle underwent low-level system hijacking and software modification. On the input side, the program bypasses the system's high-level input stack to directly read the 4096-level raw pressure sensitivity of the stylus through evdev. On the output side, a low-level intercept pad pauses the tablet's official UI process, directly taking over the exclusive libqsgepaper.so proprietary e-paper waveform engine to write frames directly to the display memory. Additionally, the project utilizes the Zhang-Suen thinning algorithm to extract the skeleton of the Dancing Script font, melting the glyph into a single-pixel wide central path to trace the pen stroke trajectory, thus perfectly replicating the dynamic handwriting playback animation stroke by stroke.

However, riddle is currently only tested on a specific system version of the reMarkable Paper Pro. Due to its requirement for root access and driver hijacking, improper operation may lead to device system damage.