Just Shikaku

Seven techniques stand between guessing at rectangles and reading a board at a glance. Just Shikaku names them, teaches each one on a real position, and then proves you know them. Shikaku hands you a grid of numbers. You carve it into rectangles until every number sits in a rectangle of exactly that many cells. The rules take a minute. Playing well takes arguments, ones with names like Prime Strips, Lone Reacher, and No Orphans, and those arguments are what this app is actually about. WHAT NO OTHER SHIKAKU HAS - A curriculum. Seven named techniques, each with its own lesson on a board where that technique is the next move. - Hints that argue. Ask for help and the reasoning climbs a ladder: a nudge, then the technique's name, then the full argument drawn on your board: the candidates that could work, the ones that die, the cell that decides it. The app can lay the rectangle for you, but…