Magic Block

Fit the digits 1 to 9 into a three by three grid so that every row and every column comes out at the number printed beside it. Each digit is used exactly once, so every square you commit to takes a digit away from somewhere else - that is the whole puzzle.

Lines are read straight through, left to right and top to bottom, with no operator precedence: 2 + 3 x 4 is twenty here, not fourteen, and the tutorial leads with that rather than leaving you to find out. A total turns green the moment its line is right, so you are never guessing whether you are close.

Twenty-four boards that open up as they go: plus and minus to begin with, then multiplication, then fewer and fewer squares filled in for you until the last four hand you nothing at all. Every board is checked by solver before it ships and has exactly one answer, so there is no second solution to find and be told is wrong.

Tap a number then tap a square, or use the number keys.