Cutting Corners

A geometric duel by Sid Sackson, from A Gamut of Games (1969). Two adjacent sides of a square are Blue's, the other two Red's. Each turn you draw an "ell" — a line straight in from one edge, one right-angle turn, straight out to an adjacent edge — that must cross an opponent-coloured line or touch an opponent-coloured edge. There's a catch that gets sharper every turn: your nth move overall must cross exactly n−1 previously drawn lines — in other words, every single line on the board so far. After six moves the square is carved into regions; whoever's colour borders more of a region's edge owns it, and most regions wins.