We recently started an experimental Sudoku game, where you can play with others together. It's actually a Twitch stream and you can play with chat inputs. For example: If you write a1,9 that means you want to write 9 into a1 (the grid is marked similarly to a chessboard). If you are curious what it's like to play Sudoku competitively and cooperatively at the same time, come and have a look, here's the link to the channel:
Currently our best time is a 2:53, and averaging about 4-5min when we have a few players. You get scores for every good number you wrote in, but you have to be the first one. If somebody was faster, he/she gets the point. Minus points if you tried to write something wrong into an empty cell.
Thanks for reading this, and have a go at it if you are interested.