Out of book message.

I think it would be a good idea to allow people the option of seeing whether or not during a standard game whether the moves they’ve played are original or not. Seeing after a certain number of moves the message “out of book” would be a good way of advancing chess theory. This way the players know whether the moves they made are part of opening theory or not. Even I get confused whether the moves I’m making in the opening is part of theory or my creative endeavors.

I think if you could see this during the game it could give an advantage to one side. For example, if your opponent goes out of book early it could be an indication that there is a tactic on the board.

You can compare your opening to the existing opening database right after the game is over.

This exists, but not quite in the way you might expect it. When you go the analysis board of a game played on the website, open the opening explorer and table base (represented by the book icon under the moves played in the game). Once opened, it will show you what the most common continuations of the current position being shown, and when you do go out of book, the opening explorer will return a message "No game found" with an option to close the explorer right underneath that dialogue.

You can also select between master games (to see the better moves) and amateur games played on the website (to see potential blunders or more dubious lines).

You might be surprised by how many people end up in almost exactly the same position that you arrived in, and just like you or me, they got checkmated before move 15. We are all getting better, and that's what's important.