[Real-Life 'Harry Potter Magic Diary': Writing Disappears on Its Own, AI Interacts with You Stroke by Stroke on Paper] According to monitoring by 动察 Beating, developer Maxime Rivest has open-sourced a project called riddle, which recreates the screenless, physical interaction of Tom Riddle's diary from Harry Potter on the reMarkable Paper Pro e-ink tablet. Users can write questions on the paper with a stylus, and after pausing, the handwriting will automatically fade and disappear. Then, a large model recognizes the image and streams back the content, with the device dynamically writing out the response in handwriting, stroke by stroke, which fades again after being read. To achieve smooth 'air handwriting' animations on the e-ink screen and reduce latency, riddle undertakes low-level system takeovers and software modifications. On the input side, the program bypasses the system's high-level input stack and directly reads the raw 4096-level pressure sensitivity of the stylus via evdev. On the output side, a low-level interception shim pauses the tablet's official UI process and directly takes over the proprietary libqsgepaper.so e-paper waveform engine to write frames directly to the video memory. Additionally, the project uses the Zhang-Suen thinning algorithm to extract the skeleton of the Dancing Script font, reducing the glyphs to single-pixel-width center paths to trace the pen stroke trajectory, thereby perfectly replicating the stroke-by-stroke handwriting playback animation. However, riddle has only been tested on specific system versions of the reMarkable Paper Pro. Since it requires root access and involves driver takeovers, improper operation may result in system damage to the device. [Original Article Link]