Fill One Line is a free online puzzle game where your goal is simple but surprisingly tricky: draw a single continuous line that covers every cell on the playing field without lifting your pen or retracing your path. Obstacles block the obvious routes, forcing you to think several moves ahead before committing to a direction. Each level is a self-contained logic challenge built around unique grid shapes and strategically placed barriers.

The game starts accessible enough for beginners, but difficulty ramps up steadily as field shapes get more irregular and obstacles multiply. The key is learning to spot dead ends before you reach them – if you cut off a section of the grid too early, you'll need to restart. There's no timer breathing down your neck, so you can pause, study the layout, and rethink your approach as many times as needed. That slow-burn satisfaction when a tricky path finally clicks into place is genuinely rewarding.

Fill One Line suits anyone who enjoys single-line drawing puzzles, one-stroke path games, or classic brain teasers that test spatial reasoning. It runs directly in your browser via WebGL and HTML5, so there's zero installation required. Whether you're looking for kids' logic puzzle games, casual one-player challenges, or a quick mental workout during a break, Fill One Line delivers clean, focused gameplay that keeps you coming back for just one more level.