Puzzle Sprint added & new Puzzle Leaderboard criteria

A new mode, Puzzle Sprint, has been added! Solve as many puzzles as you can within the time limit.

You have 3 minutes, or until you make 3 mistakes, whichever comes first, to solve as many puzzles as possible. Have fun with it! 😊

I've also added a new requirement for the Puzzle Leaderboard: if your puzzle rating is 2100 or higher, you now need a Puzzle Sprint score of at least 20 to be included in the ranking.

Thanks for reading, and enjoy the Sprint!