Only allow the user to take a specified amount of time when solving a lichess.org puzzle
lichess.org is a free and open source chess playing website.
It has a "Puzzles" feature that allows you to improve your chess skills by doing tactical exercises. You get a numerical rating based on how well you perform.
Unfortunately, there is no limit to the time you take to solve a puzzle. Ratings make more sense when speed is considered as well as accuracy.
This script displays a countdown (30 seconds default) and when the time is up, it makes the puzzle fail. Thus you have to complete the puzzle within that time limit.
The time limit is configurable in the source code (var timeout, in milliseconds).
