The Barnbougle Inheritance, Renfrew

Working method

Read a memorandum.
Tap "Mark as done" when you have carried it through.
Scan the register and tap every entry the memorandum rules out.
Strike rows by tapping them, or drag across a column to toggle every row you pass through. Drag across unstruck rows to strike them, across struck rows to un-strike. A mixed drag flips each row to its opposite.
When a memorandum clears a whole page, "Strike page" on either toolbar does it in one click. Once the page is struck the same button reads "Unstrike page", so a memorandum you take back costs one click too.
When one entry remains, the surface checks it for you and says whether it is the heir. You do not have to work the checksum by hand. The printed book asks for that only because paper cannot answer.

No memorandum is automatic. The firm believes; you observe.

What is on the screen

The register: Most of the surface. One register page at a time, laid out in the book's own columns and rows, under the same running head the printed page carries: the parish, and the register page number. An entry sits where it sits on paper, so the two can be worked side by side.
The two page toolbars: One above the register and one below it, both the same. Prev and Next at the ends, the page number and the standing count in the middle, the register controls before Next. There are two so that a reader who has worked down to the foot of a page does not have to scroll back up to say the page is done.
The memoranda drawer: The panel on the right, holding the memoranda and everything you do that is not striking. On a wide screen it sits beside the register; below 1280px it slides over it. The "Memoranda" button on the top toolbar opens and closes it either way, and that choice is remembered on this device.
The standing count: How many entries are still unstruck, shown in both toolbars and at the top of the drawer, updated after every strike. The book is finished when it reaches one.
The verdict: A line under the header that appears only when there is something to say: that the last entry standing is not the heir, or that nothing is standing at all because the heir was struck along the way. Both are corrections, so they sit out of the way of the register rather than blocking it.

Striking, four ways

Tap an entry: Strikes it. Tap it again to un-strike it. A whole book can be worked this way, one entry at a time.
Drag across a block: Press on one entry, drag to another, lift. Every entry in the rectangle between the two moves to the opposite of whatever the entry you started on was, taking in every column and every row crossed and both ends. Start on an unstruck entry and the block is struck; start on a struck one and the block is cleared. Mouse, finger and pencil all count as the same gesture.
Drag corner to corner: Press in one corner of the page, outside the entries, and lift in the opposite corner: the whole page is struck. It has to start and end off the entries, so that a large block drag is never mistaken for it.
Strike page: The button, on either toolbar, for the same thing without the gesture. It reads "Unstrike page" once the page is clear, and it posts the direction it is showing, so a second click on it never undoes the first.

Moving through the register

Prev and Next step a page at a time. The page number between them is an input: type into it and the register goes there as you type, with no need to press Enter. "Hide solved pages" makes Prev and Next skip over any page you have struck out entirely, while a typed page number still reaches it. Once every page one way is solved, that button is closed off rather than walking you back into finished work.

With that on, the toolbar reads something like Register page 29 of 53 (4 active). The parenthetical is how many pages still hold an unstruck entry, which is the set Prev and Next will stop on. Late in a book the two numbers separate, and the smaller one is the better measure of what is left.

Keyboard. n or → for the next page, p or ← for the previous, j to jump to the page box and type a number, Esc to close this.

The drawer, panel by panel

The memoranda: Every memorandum in the book, numbered as it is numbered on paper, each with its own "Mark as done". They can be worked in any order. Marking one done is a note to yourself about where you are and strikes nothing. Under each one is roughly how many entries it leaves standing, which is a check on your own pass rather than a substitute for it.
Putting them in your own order: Drag a card by its number and drop it where you want it. The order is yours and it is kept with the book, which is worth doing when two memoranda are easier to carry through together than apart. It moves nothing but the cards: the number on a card is the number printed in the book wherever it sits, so a memorandum you have moved still names the same page.
A memorandum you have finished with: Once it is marked done the card folds down to its number and its Undo button, so the list stays short without losing your place in it. Click the card and it opens again for as long as it has focus, then folds away when you click elsewhere. If you would rather they went entirely, use the box above.
Hide the ones marked done: A checkbox under the heading, offered once anything is done. It drops the done memoranda out of the list, leaving what you still have to carry through. Only the list changes: a hidden memorandum is still done, still counted in the standing line, and clearing the box brings back exactly what was there.
Check a candidate: For a hunch you want tested before the memoranda have finished narrowing. Type a register number and the answer is yes or no. Once exactly one entry stands, the same check appears at the foot of the memoranda with the printed book's arithmetic written out beside it, for anyone who would rather work it by hand.
Notes: A scratch pad that saves itself when you click away from it. In the sample it lives in this browser session, like the rest of your work.

How the solver answers you

It confirms, and it never names. Reach one entry and it tells you there and then whether you have your heir; check a hunch early and it answers yes or no. A "no" says only that this is not the one, which is exactly what the printed checksum says when the digits do not match. So you can be certain when you finish without anything ever handing you the answer, and the finding stays yours.

This is the free sample, so it needs no account and asks nothing of you. Your work lives in this browser session and goes with it; sign in and the sample is kept with the rest of your books.