Magic Square
All gamesTarget 34Filled 8 / 16Tries left 6Board wide
8 to place, 6 tries left. Holding 3. Cursor at row 1, column 2: empty. This row needs 16 across 2 cells; this column needs 11 across 2 cells.
16Row 1 holds 18 and needs 16 more across 2 cells.23Row 2 holds 11 and needs 23 more across 2 cells.18Row 3 holds 16 and needs 18 more across 2 cells.9Row 4 holds 25 and needs 9 more across 2 cells.6Column 1 holds 28 and needs 6 more across 1 cell, so that cell is forced.11Column 2 holds 23 and needs 11 more across 2 cells.15Column 3 holds 19 and needs 15 more across 1 cell, so that cell is forced.34Column 4 holds 0 and needs 34 more across 4 cells.34Every row, column and diagonal must make 34.
↘ 3Top-left diagonal holds 31 and needs 3 more across 1 cell, so that cell is forced.↗ 34Top-right diagonal holds 0 and needs 34 more across 4 cells.
Column 1 has one hole left, so it is forced: it holds 28 and 34 − 28 = 6. That is the whole technique — find the line with one hole and read the number off it.
← → ↑ ↓ (or W A S D) move the cursor · F or Shift holds the next number in the tray, Esc or Z the previous one · Enter or Space puts the held number in. Or click a cell, then click a number. A wrong number is refused and costs one try; moving and choosing cost nothing. Click the board first, or press Tab to focus it.