Chain Lines is classic Dots and Boxes on a 6×6 dot grid. Tap any faint line to claim it; close the fourth side of a box to mark it and take another tap right away. All 25 boxes get claimed and the most boxes wins. Ten campaign levels face the Pencil AI — random early, free-box aware from level 5, and a chain-counting, double-crossing endgame from level 8 — plus a daily match everyone shares, with honest world win-rate lines and a levels-cleared percentile. Flat pencil-and-paper art, synthesized tones, full English and Simplified Chinese.