Sudoku doesn't work on a tablet?

After spending at least an hour trying to sign up for the site. (No ability to copy and paste a password, for one thing.) I was finally, after a few misdirections, able to bring up the Sudoku page. Unfortunately, the game grid is unresponsive. It seems to be an image, not a text box.

Am I doing something wrong, or do I need a computer?

Thanks, Harriet