What is this puzzle, in one breath?
It is the core rule of Sumbriska, the iPhone number puzzle we make: islands have target sums, bridges carry numbers, and flipping a bridge moves its number from one island to the other. There is no arithmetic beyond single-digit addition. The skill is seeing which island is short, which is over, and which bridge fixes both at once.
- Daily: one board per calendar day, same for everyone, replayable.
- Short: five islands and eight bridges. Par is the fewest flips from the starting arrows to any valid solution.
- Honest: the solution is one tap away and nothing is tracked.
Can two solutions take different numbers of flips?
Yes. On the April 10 example, two flips solve the board. A second solution takes five. Both end with exactly the same total on every island.
See the two moves and the extra loop
Turn the 9 from island 1 toward island 2. Turn the 8 from island 5 toward island 4. The five totals now read 5, 13, 13, 12 and 4. No single move can fix all four islands that start off target.
For a second solution, send a 4 from island 2 to 3, a 4 from 3 to 4, and a 4 from 4 back to 2. Each of those islands gives away exactly what it receives. That loop explains why two different arrow patterns can produce the same totals.
See the three transfers in a diagram, or get a copy for your class or newsletter.
What happened across 365 date seeds
Honest Little Apps generated every board dated November 6, 2025 through November 5, 2026 with this web companion’s generator. For each date, all 256 arrangements were checked against all five targets. This describes the browser generator, including dates before this page existed. It measures no players, play times or native app boards.
For the 360 boards with one solution, the generator’s stored answer gave the minimum. Of the other five, only April 10 had a shorter alternative. The par above now checks all possible answers before displaying the minimum.
Download the 365 dated results (CSV) · Get the standalone checking script. To reproduce the file locally, run node reproduce-bridge-census.mjs. It needs no packages, account or network connection.
The app, annotated
The app board: islands with a target and a running sum, bridges with a number. The two green islands already match.
Two Tides: one bridge arrangement has to satisfy two schedules at once. One puzzle, two answers that must agree.
Every solved board builds your harbor. Orchard Isles is region 2, included free.
Who should pick something else
You want a race
Harbor Run in the app is timed, but the game is built around unhurried thinking. If you want leaderboards and global rankings, this is the wrong harbor.
You want hundreds of free boards today
The free download has regions 1 and 2 (20 boards each in the screenshots), the Daily board, The Deep and Harbor Run. Regions 3 to 6 sit behind the Voyage Pass subscription, and there is no free trial.
You want classic Hashi
If "bridges puzzle" means Hashiwokakero to you, where you draw bridges so every island gets a set number of them, that is a different rule. Here the bridges already exist; you decide which way each one points.
How a board goes, in three steps
Find the island that is furthest off
Compare each island's sum with its target. The biggest gap usually names the bridge to flip first.
Flip the bridge that helps both ends
A flip subtracts from one island and adds to the other. The best flips fix an island that is over and one that is under in a single tap.
Check the remainder, then the tide
The grand total always stays the same. If one island has too much, at least one other island has too little. Trace the bridges between them. In the app, Two Tides boards make you check the same layout against a second schedule.
How it compares with puzzles you already know
| Puzzle | What a move is | What you are tracking |
|---|---|---|
| Sumbriska daily board | Flip one bridge's direction | Each island's sum against its target |
| Sudoku | Write one digit in a cell | Row, column and box constraints |
| Hashi (bridges) | Draw or remove a bridge | Bridge counts per island, one connected map |
| Word-of-the-day games | Guess a word | Letter feedback across six tries |
The honest difference: sums give you continuous feedback. You are never guessing blind; every flip tells you something.
A small scene, made up
The kettle clicks off at 7:04. You have about ninety seconds before the pour and another three while it steeps. The daily board loads, five islands, one of them already green. You flip the 9 off the island that is over by nine and watch its neighbour land exactly. Two more flips, and the last island is forced. The coffee is still a touch too hot. That is the size of puzzle this is meant to be.
Questions people ask
How does the daily number puzzle work?
Each island shows a target. Each bridge carries a number and points at one island; that island counts the number in its sum. Tap a bridge to flip which island it points at. When every island's sum equals its target, the board is solved. A new board appears every day, built from the date, so everyone gets the same puzzle.
Is the puzzle on this page the same as the app?
It uses the same core rule, flip bridges to match sums, with five islands and eight bridges. The iPhone app adds themed regions, Two Tides boards that must satisfy two schedules at once, timed Harbor Run, the endless Deep, a workshop for custom boards, and a harbor you build as you solve.
Is Sumbriska free?
Yes to download and play. Regions 1 and 2, the Daily board, The Deep and Harbor Run are included. An optional Voyage Pass subscription ($4.99 a month or $29.99 a year, no free trial) adds regions 3 to 6, side boards, Gale Run, the 3-4 ring workshop and cosmetics.
Is it suitable for kids?
The listing describes child profiles with no purchases and no links, an adult area behind PIN or Face ID, no ads, no accounts and no data collection, and it works offline. The board on this page collects nothing either.
What is the minimum number of flips?
Each of the eight bridges can point two ways. The game checks all 256 arrangements, keeps those that meet all five targets, and finds the smallest number of arrows that must change from the start. That minimum is par. You can solve the puzzle using more flips.
Get Number Puzzles free
Sumbriska on iPhone: six themed regions, Two Tides boards, a timed run, an endless dive, and a harbor that grows as you solve. No ads, no account, works offline.
Sources
- Number Puzzles: Sumbriska, App Store listing, version 1.0.0, read 4 November 2026. Feature and pricing statements above come from this text.
- Hashiwokakero rules for the comparison row: Nikoli, the puzzle's original publisher.
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