Trail by Franz Enzenhofer

Trail is a quiet logic puzzle about a single unbroken line. Start at the ring and draw one line that visits every tile on the board exactly once - no crossing, no doubling back, no tile left out. Each level teaches one new idea and then folds it in with the rest: walls, arrows that force a direction, beamers that carry the line across the board, a flag that marks the end, ice you slide along, one-way doors, and keys that open locks. Every board is generated, solved and difficulty-checked from its level number alone, so level 42 is the same puzzle for everyone, forever, and there is always a solution to find. Get stuck and the line simply unwinds itself - nothing is ever lost, and you can take as long as you like. It runs fully offline, with no ads, no accounts and no purchases.