Islands float on a grid, each marked with a number. That number is exactly how many bridges must connect to it. You draw bridges between islands — straight lines, horizontal or vertical, at most two between any pair, and bridges can't cross each other. Satisfy every island's number with one connected network and the puzzle's solved. It's pure logic; there's never any guessing required.
Seven difficulty levels grow the grid and the island count. A fresh daily puzzle each midnight, shareable with a friend through the challenge link.
Corner islands are the traditional foothold — an island marked with the maximum has every one of its bridges forced, and the rest of the puzzle unspools from there. Bridges may never cross, which is the constraint that does most of the quiet work. Seven levels run Beginner to Cyborg, the daily board is shared by everyone, and Nurikabe is the natural next Nikoli-style habit after this one.
Hashi was the game that forced me to take phone screens seriously as a design constraint rather than an afterthought. On paper, this puzzle is elegant minimalism — numbered islands, straight bridges, done. On a 360-pixel-wide screen, that same minimalism becomes a usability trap: thin lines are miserable tap targets, and a mis-tap that places a bridge you didn't want is the fastest way to make someone close the tab.
So the build decisions here are all about legibility under fat thumbs. Bridges render as thick, tappable lanes with generous hit-areas around them — you're tapping a corridor, not a hairline. And because the rules say bridges never cross and cap at two between any pair of islands, the game simply blocks illegal placements instead of letting you draw one and scolding you afterward. Try to route a bridge through an existing one and nothing happens. The rules are enforced by what the interface will physically let you do, which means your attention stays on the logic, where it belongs. That's the whole philosophy: the puzzle should be hard, the input should be invisible.
The logic itself has three laws, and the mistake I see most is holding only two of them at once. Players remember that bridges can't cross. They mostly remember the cap of two per island pair. Then they satisfy every island's number and discover the puzzle won't accept the solution — because they've built two beautiful, separate networks, and the third law says the final web must be fully connected. One network, every island reachable from every other. Connectivity is the rule that turns Hashi from arithmetic into topology, and it's the one that ambushes people at the finish line.
Here's how to start a board so that never happens to you. Hunt for the forced islands first. An 8 anywhere is a gift: four neighbours, two bridges each, every one of them mandatory — draw all eight without thinking. A 4 in a corner is the same story in miniature: only two neighbours exist, so both get doubles. A 6 on an edge forces two bridges to each of its three neighbours. Every forced bridge you draw constrains its neighbours, and the constraint spreads outward like a net pulling tight. Work from the forced islands toward the ambiguous middle, and keep asking one question as you go: is my web still one piece?
The seven difficulty levels grow the grid and the island count, and the daily puzzle is identical for every player at midnight. It's pure deduction all the way down — there is never a moment where guessing is required. When the whole network clicks into one connected web, you'll know exactly why I kept this one.
Start with the islands that can only be solved one way. A "3" sitting in a corner with just two neighbours is forced — it has to send specific bridges, because there's nowhere else for them to go. The high numbers on edges and in corners are your anchors; place their forced bridges first and the puzzle starts to skeleton itself.
From there it's the "maximum possible" rule. For any island, count the most bridges it could send to its neighbours; if that maximum exactly equals its number, every one of those bridges is mandatory — draw them all. And keep checking the no-crossing constraint, because a bridge you're forced to draw will often forbid another, which forces the next. The whole puzzle unzips from forced move to forced move. You never have to guess — if you're guessing, look harder for the move that's already certain.
Hashi is deduction in its purest form — there's no luck, no guessing, only "this must be true, therefore that must be true." It's the closest a casual puzzle gets to writing a proof. My own way in is to start from the corners and build outward. A corner island has the fewest directions it can possibly send bridges, so it's usually the most forced spot on the board — nail those down and the rest of the puzzle has something solid to grow from. It's a small lesson that travels well: when a problem feels overwhelming, find the corner that can only go one way, start there, and let the certainty spread.
You build the habit of finding the certain move instead of the convenient one, and of trusting that a hard problem yields to patience rather than luck. The bigger grids stack more constraints so the chain of deductions runs longer. No download, no sign-up — play in your browser on any device. If you like pure logic, try Nurikabe next.