CrossSheet is a plugin for creating and completing crossword puzzles collaboratively using Google Sheets. It adds a new sub-menu to Google Sheets which provides a number of ways to create and import crossword puzzles. Once an option is selected and configured, the application then converts the current sheet into a copy of the chosen crossword. 

The advantage of using Google Sheets for crossword puzzles is that crosswords can be completed collaboratively, as well as making use of the advanced formatting allowed by Google Sheets.