Disable dig pw actions if no resources
Don't allow the dig and double dig power actions if the player doesn't have the resources to build a mine after the dig.
A game I played had a new player lose 5pw cos they didn't realise that they didn't have the resources to build a mine without doing free pw actions.
This is tough because it can basically be used to pass a turn and get another booster. And you can undo the move instead of clicking "End turn".