Three kinds of board
DIGIGMA has six live games. This article compares three of them: Sudoku, Killer Sudoku and Binary Puzzle. They share a contract: one finished grid, reached by reason, with no need to guess. They do not share a feeling. You notice it in the first minute. The eye looks for different kinds of necessity.
This is not a rule sheet. The rules live in How to play. This is a way to tell the three sits apart so you can pick the one you actually want tonight.
Sudoku — placing a digit
Sudoku is the familiar 9×9. Some cells are already filled. Those stay. Your work is to place 1 through 9 so that every row, every column, and every 3×3 box holds each digit once.
The sensation is placement. You look for the last empty cell in a group, or a digit that has only one house left. The grid is large enough that a single scan is never the whole story, and small enough that the next forced cell is usually nearby. Draft marks shrink. The last few digits fall in with a quiet click you can feel without hearing it.
If you already know this board, start here. The DIGIGMA version is only the classic size — 9×9, not a zoo of variants. How to play Sudoku. Sudoku grids.
Killer Sudoku — cages and totals
Killer Sudoku uses the same 9×9 and the same “once each” laws. The clues are not given digits. They are dashed cages, each with a printed sum. The cells in a cage add up to that number, and a digit cannot repeat inside the cage.
The sensation is combination. You still hunt singles, but you also ask what few sets of digits can make 17 in three cells, or 3 in two. A cage that can only be 1 and 2 tells the rest of the box what to avoid. Arithmetic stays small and local. You are not doing a spreadsheet. You are noticing that two constraints have shaken hands.
People who like Sudoku and want a different tightness often land here. The grid looks emptier. The work is not emptier. How to play Killer Sudoku. Killer Sudoku grids.
Binary Puzzle — two symbols, four laws
Binary Puzzle is 0s and 1s on a 6×6 or 8×8. Each row and each column has equally many of each symbol. No three identical sit in a line. No two rows match; no two columns match.
The sensation is balance and uniqueness. A pair of 0s forces 1s on the open sides. A line that already has its half fills with the other symbol. Near the end, uniqueness matters: a finish that would copy another row is illegal even if the counts look fine. The alphabet has two letters. The sentences are strict.
The smaller grid is a shorter sit, not a lesser one. If you want something that is not 1-through-9, this is the board. How to play Binary Puzzle. Binary Puzzle grids.
Same contract, different sit
In all three, the givens — or the cages — decide a single ending. You do not choose among worlds. You find the one that is already there. That is why a guess feels like leaving the work, on Sudoku as on Binary Puzzle. We wrote about that in A unique solution.
When one family goes stale, open another. The scans transfer more than the patterns do. Forced cells first. Clean marks. Read the group that is almost full. The rest is flavour: digits, cages, or 0s and 1s.
If you are choosing rather than comparing, Which game to open first is the practical page. Easy is the honest first band on all three.