How many pieces hit a square — fast enough that the answer arrives before you have finished asking.
Not started
clean = right, and inside the cap
What this unit is for
Every question in the seeds course reduces to this one. Is that piece loose?
is "zero defenders." Is it underguarded? is "more attackers than defenders." If counting
is slow or wrong, everything built on top inherits the error and you never find out where it
came from.
So the target is not accuracy. It is accuracy under a clock.
Counting correctly in forty seconds is not board vision — in a real game that budget is already
spent on something else.
Not in this unit
Whether a capture is good. Counting comes first.
Tactics, motifs, or seeds. Those need this unit finished.
Legality. A pinned piece still attacks what it attacks.
Block 1Read · ~8 min
The rules
Rule 1A piece attacks a square if that square is one it could capture on. Two things never change the answer: what is standing on the square, and whether moving there would be legal right now — a pinned piece still attacks everything it attacked before it was pinned.
Rule 1aWhat does change the answer is how the piece captures. Every piece except the pawn captures exactly the way it moves. A pawn does not: it moves straight ahead and captures diagonally, so it attacks only the one or two diagonal squares and never the square directly in front of it. A king attacks all eight neighbours, never the square it stands on.
Rule 2A queen, rook or bishop stops at the first piece in the way. If anything at all sits between it and the square, it does not attack that square.
Rule 3Unless that piece is one of yours that attacks the same square. Then both count: a rook behind a rook on an open file, a queen behind a bishop on a diagonal. This is a battery, and the piece behind is an x-ray attacker.
Rule 4The last quarter of this unit names the square instead of marking it. Nothing else changes. A ringed square does unit 1's work for you, so counting one only ever tested half the skill — in a game nobody outlines the square you are worried about.
Rule 1 versus rule 1a
These pull in opposite directions and the difference is worth holding onto. Legality is about this position: a pin, a check, a king that would step into danger. Ignore all of it. Capture geometry is about the piece itself and never bends — a pawn cannot capture forwards in any position, so the square ahead of it is not attacked, not even a little.
Block 2Do · ~20 min
Practice — ten positions, with the answer shown
The clock runs but nothing is at stake. Feedback is full at first and thins out, so by the last three you get the answer and nothing else.
Block 3Do · ~12 min
The check — twenty positions you have not seen
Drawn fresh from a held-out pool, so a retake is a new set rather than a memory test. No feedback until the end.
The gate is 18 of 20, each inside its cap. Two misses is not generosity — it is the width of a bad day. A third means the rule has not automated yet, which is a reason to keep drilling and not a verdict about you.
Block 4Ask · open-ended
The misses are the useful part
Add anything you got wrong, or got right and did not trust. The button below assembles every added position into one block of text and copies it. Paste it into the tutor project and argue about it.
Ask for the rule, not the answer
You already have the answer; it is in the packet. The question worth asking is which rule you applied wrongly, and whether the mistake was the rule or the reading. Those need opposite fixes — a misremembered rule gets restated, a misread board gets drilled.