Score
0
Time
150s
Best
—
Logic puzzle. Shade cells so that every row and column total matches its clue. Each cell is worth its column's value (shown on top) toward the row total, and its row's value (shown on the left) toward the column total. Solve as many as you can in 150 seconds.
The grid has a number above each column and to the left of each row — these are the cell values, 1 up to the grid size. Along the right edge is each row's target total; along the bottom is each column's target total. Tap a cell to shade it; tap again to clear it.
A shaded cell adds the value printed above its column to its row's running total, and the value printed to the left of its row to its column's running total. Your goal is to shade exactly the right cells so that every row's total equals the clue on its right, and every column's total equals the clue at its bottom, all at once.
The clue turns green when that row or column hits its target exactly, and red if you have gone over, so you can read your progress at a glance. Solve a grid and the next appears instantly. Solve as many as you can before time runs out.
Start with the extreme clues. A row or column whose target is 0 has no shaded cells at all — leave its whole line blank, which immediately removes those cells from the crossing totals. At the other extreme, a target equal to the maximum possible (every cell shaded) forces the entire line on. Both ends give you free, certain moves before any real thinking.
Think of each clue as a subset-sum. For a row, you need a set of column-values (1, 2, 3, …) that adds up to the target; small targets have very few combinations. A row target of 1 can only be the first cell; a target of 2 only the second; a target of 3 is either the third cell alone or the first two together — and the column clues usually decide which.
Let the two directions cross-check each other. Once a few cells are forced by row logic, recompute the column totals: a column that has already reached its target means every other cell in it must stay blank, and a column still short by exactly one value points straight at the cell that supplies it. Bouncing between rows and columns is the heart of the solve.
Use the colour feedback as a checklist rather than guessing. Shade the cells you are sure of, watch which clues turn green, and focus on the lines still showing a number. A clue that turns red tells you instantly to remove a cell — usually the largest-value one you just added.