101Weiqi (101围棋网) is a popular Chinese weiqi site. It is best known for its complete, well-maintained problem collection. Besides, it also has features such as playing games, downloading kifus, pattern search.
Only Chinese-language access is provided on the site, but a guide has been produced detailing navigation for English speakers.
Users can submit new problems to the site, rate a problem, add new lines to a problem and leave comments. When a new problem is submitted, it takes time for admins to verify its validness and add it to the pool. In August 2021, there were 129,385 problems in use, 67,586 waiting to be approved to enter the pool and 38,239 removed from the pool. Each problem is assigned a difficulty level which ranges from 15kyu to 7dan.
There are currently 3 major categories of problems: life and death, tesuji, semeai. Other categories include capturing, trick play, appreciation, opening, endgame, midgame, emulation, guess next move, theory.
Users can access problems in a variety of forms: Daily, Skill test, Single problem, Homework, Collection, Battle.
Daily problems: Eight problems of varying difficulty are featured on the front page daily, from around 10 kyu up to 6 dan. Click a problem to attempt it.
Skill test（棋力测试）: Select a level from 15 kyu to 7 dan and you will be given a set of 10 problems roughly around that difficulty from categories life and death, tesuji and semeai. Each problem can only be attempted once and has a time limit of 45 seconds for the whole sequence. Success is achieved if at least 8 out of 10 problems are solved. Clearing a level for the first time will unlock the next level. Also called "guan" by the English-speaking community because it appears in the URL.
Single problem（做一题）: Also known as the rating mode. As the name suggests, a single random problem is provided. The number of attempts (one or two), time limit, difficulty, and type of problem provided can be set in the Single problem settings page (or the link 做一题设置 near the top of the problem page.)
Battle（巅峰对决）: A 1v1 problem solving challenge against another user. The players are given problems; solving one will advance their marker around a circle, and the player that catches up to their opponent's marker (by solving more problems faster) wins.