Numberlink (also known as Flow Free) is a globally beloved line-drawing puzzle — on an N×N grid, draw paths connecting each pair of matching numbers (or colors). Paths cannot cross, cannot overlap, and must fill every cell on the board. Simple enough for a 5-year-old to understand, yet large puzzles can stump math PhDs.

MeTool Numberlink offers 100+ handcrafted levels, from 5×5 tutorials to 9×9 expert challenges, across five difficulty tiers (Tutorial → Easy → Medium → Hard → Expert). Every level has a unique solution, guaranteeing fairness. Canvas-rendered smooth line drawing, auto-saved progress, one-tap solution verification — everything runs locally in your browser. Zero sign-up, zero download.

100+ curated levels, five difficulty tiers: Tutorial levels use small 5×5 grids to teach the rules quickly. Easy and Medium are great for daily relaxation. Hard and Expert use larger grids with more colors, testing your spatial planning and deep logical reasoning.

Guaranteed unique solutions: Every level is algorithmically verified to have exactly one correct answer. No guessing required — if you've filled every cell with non-crossing paths, you've found the solution.

Canvas smooth line drawing: Drag your finger or mouse across the grid to draw paths, rendered in real-time on Canvas with vivid colors and fluid strokes. Clear a single color or reset everything with one tap — intuitive and natural.

Auto-saved progress: Your completion progress is automatically stored in localStorage. Come back tomorrow and continue right where you left off. A progress bar shows your overall completion rate.

Pure frontend, zero privacy concerns: All logic runs locally in your browser — no data transmitted, no account needed. Open the page, pick a level, and start connecting.