About Zip Game

Why I Built This

I've been hooked on path-drawing puzzles since long before "Zip" had a name — the kind of number-and-grid logic games that turn up in puzzle magazines and get scribbled out on graph paper during a slow night of board games with friends. There's something addictive about a puzzle with exactly one correct answer, solvable by logic alone, with no luck and no clock forcing your hand. When LinkedIn's daily Zip puzzle brought that feeling to a much bigger audience, I wanted more of it than one puzzle a day — so I built this: a free, no-signup version with a fresh daily puzzle, unlimited practice at any difficulty, and a full archive to catch up on any day you missed.

What Zip Really Is: A Hamiltonian Path

Strip away the numbers and the grid, and Zip is a playable version of one of graph theory's most famous problems: the Hamiltonian Path Problem — finding a path through a graph that visits every vertex exactly once, with no repeats. Every cell on a Zip board is a vertex; the line you draw is that path. The numbered clues just pin down which order a handful of those vertices have to be visited in along the way.

That's also why generating a good Zip puzzle isn't trivial. Finding a Hamiltonian path on an arbitrary grid is an NP-complete problem — as the grid grows, or more walls get added, the number of possible routes explodes, and there's no shortcut formula that spits out an answer directly. Solving (and generating) these puzzles leans on the same tools computer science uses for the general problem: depth-first search and backtracking, pruning dead ends as they're found.

Where Zip Comes From

Zip isn't a new invention — it's a streamlined descendant of two much older pencil-and-paper puzzle traditions. The closest ancestor is Numberlink, a grid puzzle popularized by the Japanese puzzle publisher Nikoli, where you connect matching pairs of numbers with non-crossing lines. The other is the "Snake Pit" style of puzzle, which adds the constraint of filling the entire grid, not just connecting pairs.

LinkedIn's version simplifies and merges both: instead of connecting several separate pairs of matching numbers, Zip asks for one continuous path that visits 1, then 2, then 3, and so on in strict sequence — while still, like a fill-the-grid puzzle, requiring that single line to pass through every cell on the board. That one change turns a puzzle about several independent connections into a single unbroken route, which is a big part of why it reads so cleanly on a phone screen and can be picked up in seconds.

What You'll Find Here

Every mode runs entirely in your browser — no account, no download, and nothing collected beyond what's explained in our Privacy Policy.

Get in Touch

Questions, bug reports, or just want to talk about Hamiltonian paths? Email me at [email protected].