⬤ Villager Connect Four

That Master-level librarian drives a hard bargain. They have also solved Connect Four, and they are going first.

Open any villager's trade screen and hit Connect Four. A full board opens right there - no items, no commands, no setup.

The villager goes first, and that is the point

Connect Four is a solved game. On the standard 7×6 board, the player who drops first can force a win - proved by exhaustive computation, not just observed. Whoever moves first is playing a won game.

So the villager gets it. That means a Master villager isn't "very strong": it is unbeatable, and no amount of skill changes that. If you'd rather have the winning side, one line of config hands it to you - see below. Your colour follows the turn order, so whoever drops first plays yellow.

How strong are they?

A villager's trading level sets its strength - and each level thinks in a genuinely different way, not just deeper:

Villager level	Connect Four strength
Novice	Drops almost at random - won't take a win, won't block yours
Apprentice	Takes the win in front of it, blocks yours, sees nothing further
Journeyman	Never plays into a loss; makes and spots double threats
Expert	Understands odd/even threat parity
Master	Has solved the game

The jump from Journeyman to Expert is the interesting one. Every column holds an even number of cells, so in a pure filling race the first player takes the 1st, 3rd and 5th cell of a column and the second player takes the 2nd, 4th and 6th. A threat is therefore only worth something if its row falls to its owner - the same three-in-a-row one row higher can be worthless. A Journeyman counts threats. An Expert counts the ones that will actually be reached.

How to play

• Click a column - or anywhere above it. A ghost disc hangs over the column you're pointing at.
• A full column flashes red with a dull note rather than quietly ignoring you.
• The winning four are outlined and the rest of the board dims, so a win is visible rather than inferred.
• Resign with the button, or just close the board. Walking more than 16 blocks away, the villager dying, or disconnecting abandons the game.
• No stakes, no rewards - just for fun (and bragging rights).

Configuration

config/villagerconnectfour.properties, written on first run and documented inline:

• first-player=player - you drop first, and get the theoretically winning side. The sanctioned way past an unbeatable Master.
• board-size=7x6 - anything from 4x4 to 8x7. This changes the value of the game, not just its scale: several smaller boards are draws with perfect play, so a Master can be held on those.

Under the hood

• A from-scratch pure-Java engine. The board is two bitboards packed into a single 64-bit word, one column per seven bits - the spare bit per column is a sentinel that is always empty, and it's what lets four-in-a-row be found by and-ing the board with shifted copies of itself with no edge checks at all.
• Scores are counted in discs on the board rather than plies from the search root, which makes them absolute facts about a position. One transposition table is shared by every game on the server, so a Master's knowledge compounds through a game instead of starting cold on every move.
• Fully server-authoritative - the server owns the game; the client sends a column and nothing else.
• The engine thinks on a background thread, so the server never stalls.
• Zero art: board, discs, holes and highlights are all drawn procedurally and stay crisp at any size.

Compatibility

Plays nicely with the other Villager Games mods - the trade-screen buttons stack instead of overlapping.

Requires Fabric API. Client and server both need the mod.