A fortress is an impregnable formation in which the weaker side holds the draw despite the missing material. With opposite-coloured bishops fortresses are especially common: the defending bishop controls the squares of one colour and the pawns simply cannot get through.
Here White is two pawns up (c6 and f3) with the king on e4 and the bishop on d7, but Black's bishop on c7 builds a fortress together with the king. White to move, and it is a draw (per the tablebases): the defence cannot be breached.
The main lesson: with opposite-coloured bishops, material counts for less than the blockade. Before assessing «extra pawns», check whether the opponent can build a fortress on their own colour.
Drag a piece onto the board, or click a piece and then click the squares. The cross beside the pieces sweeps every piece of that colour off the board, and a single piece can be dragged off the edge.
The pieces will be arranged into the chosen pattern.
It is the mating side to move. Find mate in one.
Openings, endgame positions and breakthrough studies - the set-up appears on the board.
A set-up in which bishop and king cover every breakthrough square, and the opponent cannot improve even with extra pawns.
Often even two: if the weaker side gets the bishop onto the right diagonal in time and blockades the pawns.
Create a second passed pawn on the opposite wing - only play on two wings usually breaks such a defence.
Build your own position in the board editor, read up on the rules of chess or run a tournament on your own positions in the free app.
Pairings are computed by bbpPairings, an open-source engine implementing the Dutch system by FIDE rules: score groups, floats on an odd field, colour alternation. Free to use.
proper rounds with correct pairings, not random matchups
a full circle, with the round count derived from the field
a light format with no tournament machinery
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