I'm nine19een.

I'm a second-year computer science student. I build useful things with AI coding tools, explore AI agents, and lead my university's competitive programming team.

CanvasCast

Draw, present slides, and record your explanation in a desktop browser.

Course details with abbreviation and colour choices

课序 / Schedule

Import your timetable and check your classes, even offline.

Glowing Christmas tree with a star, lights and ornaments

Gesture 3D Christmas Tree

Control a 3D Christmas tree with hand gestures.

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Writing.

Articles in Chinese

Lessons from Agent Harness Lab

Notes from a small coding-agent experiment: how the harness shapes behavior, how I evaluated the results, and what the experiment could—and could not—show.

My Video-to-Handout Tool Quietly Skipped Half a Lesson

A project reflection on missing material in generated handouts, and why checking intermediate outputs matters as much as the final document.

Combinatorics: Notes and Derivations

A study note connecting modular inverses, derangements, binomial coefficients, and Catalan numbers through their derivations.

AtCoder ABC457-E: Interval Coverage and Offline Fenwick Trees

From an exact-coverage condition to two interval structures, then endpoint searches and an offline Fenwick tree. A walkthrough of the modeling and implementation.

Automating My GitHub Profile with a README Generator

Turning a manual GitHub workflow into Python scripts that standardize solution comments and generate a README table, with notes on Git setup and encoding pitfalls.

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