Sum Cut

The basics

Tap a number to cut it; tap it again to keep it. The target at the end of each row and column turns green when that line is exact, stays warm while the line still adds to too much, and goes grey when it adds to too little; the small number under the target is the line's current sum. Undo steps back one cut, Hint fixes one cell from the stored answer and counts itself, Restart puts every number back, and the arrows in the top bar move between boards. The Easy / Medium / Hard chip switches size, and the HUD counts cuts, matched lines, time and hints. Your best time per board is kept in this browser only. Add ?puzzle=7 or ?level=hard to the address to pin a board.

Objective:

Cut numbers out of the grid until every row and every column keeps exactly its target sum. Each row and each column shows its target at the end of the line. The board starts with every number in play: tapping a number cuts it, and tapping it again puts it back. The board is won when all rows and all columns add up to their targets. There are 36 boards — 5×5 on easy, 7×7 on medium and 9×9 on hard, twelve of each. Every board was checked before shipping to have exactly one answer, so a fully matched board is the intended solution rather than one of several.

Controls:

Tap or click a number to cut it and tap again to restore it. Buttons: previous / next board, the size chip (Easy / Medium / Hard), Undo, Hint, Restart and Rules. Keyboard: U undo, H hint, R restart, N next board, Left / Right arrows change board, Esc closes the rules. Every button is at least 26 px tall, the board uses touch-action manipulation so a tap never zooms or scrolls the page, and it rescales to the 348×261 phone frame, the 390×844 portrait frame and the 894×670 desktop frame.