One company in Ås, and one app.

One person, from first sketch to the store

Deep River AS publishes software for Android, and the designing, writing, testing and upkeep of it are one person's work from end to end. Since there is nobody to pass a message along to, the person who reads yours is also the person who then opens the editor.

Logic puzzles are what comes out: a rulebook of two or three sentences, and a slope shallow enough to do the teaching unaided. Networks improve nothing about a puzzle, so there is none; accounts tell a puzzle things it has no business learning, so there are none of those either.

Look for a claimed outcome, a success metric or a growth promise on this page and you will come up empty — none is made, for this company or for anybody else. What there is: a company, and an app.

The entry, as it stands

An aksjeselskap is the everyday Norwegian limited form. Capital goes in before any trading begins, the company alone carries the liability, and a set of accounts is lodged each year whether or not the year contained anything worth reporting. You are asked to believe none of those lines: Brønnøysund holds every one of them.

Writing in

There are two boxes rather than one. Company matters belong at post@deepriver.space; everything about Perle — a bug, a board that misbehaved, a query about what gets stored — belongs at perle@deepriver.space. Both are read by the same pair of eyes, so the split is for filing and nothing else.

Either Norwegian or English is fine. Since no receipt is generated automatically, two working days without a word almost always means the mail never landed rather than that it is waiting its turn — try again.

Perle

A Masyu loop puzzle, laid out like pearls on a jeweller's felt. One closed loop has to thread through every pearl on the board, under two rules that look simpler than they are: at a white pearl the loop passes straight through but must turn in the cell immediately before or after; at a black pearl the loop turns a corner, and must then run straight for at least one cell on either side of it.

A check confirms that each board admits one solution and no second, which removes guessing from the game entirely. There is no connection, no sign-in and no advertising anywhere in it, and those three absences together are why the privacy policy turned out as brief as it did.

Every closed loop turns right four times more than it turns left

Here is a fact about loops worth walking rather than taking on faith. Pick one of the threads below and step round it. At each corner the walk tallies which way it went.

The ring has four corners and every one of them turns the same way: four right, none left. The strand has twenty corners and wanders all over the felt — twelve right, eight left. The counts change completely and the difference does not budge. Walk any closed loop drawn on a grid, however long or tangled, and the right turns will exceed the left by exactly four. The reason is that going once round brings you back facing the way you started, and the only way to do that with right angles is to accumulate a full turn — four quarter-turns, no more and no less.

How it was checked: the four threads above were each confirmed to be genuinely closed and non-self-touching, then walked corner by corner with the turn at each taken from the cross product of the incoming and outgoing directions. Beyond those four, 3,888 further closed loops were generated at random, with anywhere from 4 to 32 corners apiece, and every single one came out at exactly four. Not one exception appeared.