Filling Lines demands weaving non-crossing lines between identical symbols in exact order to saturate the board. Analyze layouts for viable paths, prioritizing bottleneck pairs to avoid gridlock. Difficulty evolves through larger canvases, decoy tiles, and time pressures in challenge modes. Achievement badges mark perfect solves, with global leaderboards for speed. Intuitive touch dragging feels natural, while subtle grid highlights aid planning. This sophisticated puzzler delivers profound replayability via layered mechanics and the irresistible satisfaction of immaculate, all-encompassing networks.