Now, only the empty squares contain a GestureDetector.
The GestureDetector is not necessary anymore in squares with pieces
because the tap is started when the drag is started.
This adds an option to dragging-and-dropping which is slightly hard on
smaller screens.
Fix promotions when tapping and fix handling of subsequently tapping two pieces of your color
Cancel tap if a drag is started (tapped square will not stay red in case a drag is started)
Change url strategy back to the hashtag thing
Change version
Fix bug that would not allow a piece move if you tried to take an opponents piece.
Fix the coloring of the last move after an invalid move was played.
Upgrading deps
Additionally, we set some groundwork for storing the game data (lobby
id, player id, passphrase) in permanent storage in order to reconnect
with it later.
