Math Crossword: Number Puzzle

Math Crossword is a crossword made of numbers. The grid has sums instead of
clues, and the digits you place have to make every one of them true at once.

Tap a tile in the tray, tap a square, and it goes there. Tap the square again to
take it back. Every row across and every column down has to come out right, and
because the two cross, a digit you place for a row is also part of a column.
That is the whole game, and it is why it is a puzzle rather than a worksheet.

EVERY BOARD HAS EXACTLY ONE ANSWER, AND WE COUNTED

300 levels plus 120 daily puzzles, and every one was checked twice before it
shipped: once by the solver the game reasons with, and once by a separate
counter that shares no code with it. A board is kept only when both agree there
is a single way to fill it.

So there is never a moment where you are choosing between two answers that both
work. If your grid holds, it is THE grid.

NOTHING NEEDS A GUESS

A board is also only kept if it can be reasoned out, one forced square at a
time, from the numbers already printed. There is always a line somewhere with a
single gap left in it. Finding that line is the skill, and it is a skill that
grows: by the last chapter no row and no column is enough on its own, and you
have to read one against the other.

THE ARITHMETIC IS THE ARITHMETIC YOU LEARNED

Times and divide happen before plus and minus, and the game shows you a worked
example the first time a board needs it. Digits run from 1 to 9, and division
is exact, so what is true on paper is true on the board.

300 LEVELS, EASY TO EXPERT

Plus and minus, Times and divide, Three across, Order matters, Rows and
columns, Four across, Long lines, and The deep end.

Every board was graded by playing it, not by counting its blanks. Chapter one
finishes itself if you read one line at a time. By The deep end a square can
sit with five possible digits until a column you have not looked at rules four
of them out. The curve is measured, and it is checked on every build.

A NEW BOARD EVERY DAY

The puzzle of the day is the same board for everybody, keyed on the date. Play
it and your run of days goes up. Miss one and you get one chance to carry the
run on, then solve today's board to keep it. There are 120 daily boards before
one comes round again.

HELP, ON YOUR TERMS

Two helps: reveal a cell, and open the next board. Each one is offered on the boards where it would do something, and on those boards it is
never withheld: what you are holding has no say in what you are offered. Take
one by watching a short advert, or spend gems, which arrive free from the
daily gift and from the ten ranks. Every button that costs an advert says AD on
it before you press it, and declining one takes nothing away.

Coins are separate and buy colour: five themes for the board, from Paper to
Ink. Coins never buy help and gems never buy colour. Neither one buys the
other, and coins can never be bought with money.

Undo is free and uncapped. Start again is free. Nothing is ever taken away for
finishing a board without help.

ADVERTS, SAID PLAINLY

A short advert can play when you leave a finished board, never during one, and
there is a banner under the board. Everything else is an advert you choose,
marked AD. Remove ads takes the first two away.

NO NONSENSE

No timer. No lives. No way to lose a board.
No account, no sign up, no email.
Plays offline. The boards are in the app, not on a server.
Your progress stays on your device.

Whether you call it a math crossword, a number crossword or a math puzzle
game, this is the one where the answer is provably the only one.

Free. Good luck with The deep end.