What is the daily sudoku?
At midnight a new sudoku arrives, and that day everyone plays the same one. Free in your browser, without installing anything or making an account. It starts just for you: no room, no name to fill in. Want to do it together? The share button turns it into a room, and your digits come along.
The level depends on the day of the week. Monday starts very easy and it builds up to expert on Friday; on the weekend it gets a little calmer again. The tile shows which level is waiting today, so you know what you are getting into.