Juicers
squeeze out the mate
Take the #1 spot
- #1 🦓 you 🦓
Chess
DAILY CHALLENGES
More about JUICERS
Juicers: Extra Pieces, Fewest Moves
Juicers is a free daily chess game on Quizebra in which you play White against a computer opponent from a position where you have more material than it does, and your score is the number of moves you need to checkmate it. Everyone in the world gets the same position and the same opponent each day, so the leaderboard compares like with like: whoever mates in the fewest moves tops it.
Why Is It Called Juicers?
Juicers is Hikaru Nakamura’s word for the pieces that are not pawns, and this game gives you more of them than the computer has. It is not a known chess variant: it was built for Quizebra, ordinary chess rules from an unusual, symmetric starting position. If you know odds chess, where a stronger player gives up material, this is the reverse: you have the odds, and the question is how fast you convert them.
How Do You Play Juicers?
Tap a piece, then tap the square you want it to go to. Legal squares light up when a piece is selected, so you cannot make an illegal move. The computer thinks for a moment and answers. Your move count is shown above the board throughout, and the game ends at checkmate, stalemate, a draw by repetition or the fifty-move rule, when you give up, after eighty of your moves without a mate, or as soon as you no longer have enough material to checkmate at all. The final position stays on the board for a moment with the reason, then your result appears.
Only a checkmate goes on the leaderboard. If the computer mates you, or the game is drawn, or you give up, the day’s attempt is over and your result is recorded off the board. You get one ranked attempt a day; after that you can keep playing practice positions without limit.
What Does the Starting Position Look Like?
Both kings stand on their usual squares, e1 and e8. Your pieces stand on your second rank, where the pawns normally start, and the computer’s stand on its seventh. Each side has two, four, six or eight pieces of exactly two kinds, half of each, placed symmetrically, and the two sides never share a kind of piece: if you have rooks and bishops, the computer does not. Pawns count as a kind of piece; yours promote to a queen when they reach the last rank, and the computer chooses its own promotions.
Material is counted the ordinary way, nine for a queen, five for a rook, three for a bishop or a knight and one for a pawn, and you always start eight to twelve points ahead. Two more rules keep the start fair: nobody is in check, and neither side can give check with its first move.
Who Is the Opponent?
The computer is Lozza, an open-source chess engine written in JavaScript, running in your own browser rather than on a server. It searches to a fixed depth on every move, starts each search with a clear memory and never uses a clock, which is what makes it the same opponent for everyone: given the same position and the same moves from you, it always answers the same way, on any phone or computer. It is a strong defender for these positions, far stronger than a casual player, but it is not at full strength, so the puzzle is winnable with care.
How Are the Positions Chosen?
Every position that the rules above allow was generated, and each one was then played out five times by the engine against itself, with the attacking side varied a little each time. Only positions the attacker checkmated in all five games are used, so every daily position is known to be winnable against this exact opponent. Positions where the defender could hold a fortress, or where the material advantage turned out to mean nothing, were discarded.
The middle result of those five games is the position’s par, shown on your result screen beside your own move count. There are 509 positions, with pars from 6 to 62 moves. Beating par means you did better than the engine did against itself.
Tips for a Faster Mate
Bring the king out of the way and use your extra material to take squares from the enemy king before you hunt it. The computer defends stubbornly, so a quick direct attack usually costs a piece to a fork or a pin, and a lost queen can turn a winning position into a draw.
Trade when you are ahead. Every exchange leaves the defender with less to hold on with, and a simple ending with one extra piece is often mated faster than a crowded board.
When Does the Daily Position Reset?
A new position arrives at midnight London time, with a fresh leaderboard, and everyone in the world gets the same one. Free, no account, no ads.
The other chess games are Horde, Mate in One and Mate in Two, and the best player across all four each day is the Daily ChessWhiz.
The chess pieces are Chessnut by Alexis Luengas (Apache 2.0), with the bishop from the cburnett set by Colin M.L. Burnett (BSD), slightly altered. The engine is Lozza by Colin Jenkins, MIT licensed.