Fill Line : one line puzzle game

Drag from the glowing block and snake through every tile exactly once—one wrong move and you're stuck.

There's a quiet kind of rage that builds when you're four tiles from the end and realize you've painted yourself into a corner. Fill Line drags that feeling out of you on purpose. Most puzzle games hand you a solution. Fill Line hands you a grid of tiles, a glowing start block, and a single rule: cover every tile, never cross your own line, never touch a filled tile twice. That's it. The first few levels feel like a friendly nod. By level 20, you'll be staring at a rectangle of doom, retracing steps in your head like a detective. I got stuck on a level shaped like a squashed hourglass. The obvious route loops you into the narrow waist and leaves two isolated corners inaccessible. I tried it five times. The sixth time, I started my line backwards from the far end in my head, and it clicked—sometimes the solution is to ignore the obvious starting path and commit to a longer first move. That's the whole game's brain teaser: planning ahead because you can't undo a drawn line. If you lift your finger too early, you have to restart the level, but at least there's no timer or move limit; you can sit and think as long as you like. The visuals are clean—flat colors, simple grids, no distracting animations. It works fine on a touchscreen with your finger or with a mouse. There are a lot of levels (I lost count around 80) and they ramp from tiny 3x3 grids to sprawling asymmetrical shapes. It won't replace something like a Sudoku app for depth, but for a five-minute brain break between classes or meetings, it's surprisingly hard to put down.

Start at the designated block. Drag your finger to fill all the remaining blocks. The Catch: You cannot overlap lines or revisit a block you’ve already filled!

Work backwards from the last block to find forced moves. Corners with three open neighbors are dangerous—approach them last. If a tile has only one viable entry and exit, treat it as a corridor, not a choice. Don't lift your finger until you're 100% sure; there's no undo. Zoom out mentally: odd-shaped levels often have a single long winding path.

Q: Is Fill Line free to play? A: Yes, it's completely free online; no paywalls or premium levels. Q: Can I play Fill Line on my phone? A: Yes, it works in mobile browsers with touch controls—just drag your finger. Q: Do I need to download an app? A: No download needed. It runs in your web browser as an HTML5 game. Q: Is there an undo or restart option? A: There's a restart button to reset the current level, but no undo for drawn lines. Q: How many levels are there? A: The game includes a large set of levels that increase in difficulty as you progress. Q: Does Fill Line require an internet connection? A: You need internet to load the page, but the game plays smoothly once loaded.