What Is Easy as ABC? Rules, Example, and Tactics

What is Easy as ABC and how it works

The tidy explanation of what is Easy as ABC goes like this. You have a square grid, and you must place a small set of letters, often just A, B, and C, into the cells so that each letter appears exactly once in every row and exactly once in every column, which already makes this a Latin square in disguise. Because the grid is larger than the number of letters, some cells stay empty; in a 5x5 grid using three letters, each row holds A, B, and C plus two blank cells. The clever part lives on the border, where clue letters sit around the outside of the grid. Each clue names the first letter you would meet if you looked along that row or column from that side. A clue is not about the nearest cell, it is about the nearest filled cell, so blanks can hide a letter from the edge, and that single idea of first letter seen is the entire engine of the puzzle.

A worked example

Say a row has the clue A on its left side. The very first non-empty cell you reach scanning rightward must be an A, though it does not have to be the leftmost cell, because a blank could sit in front of it, so long as no B or C appears before that A. Now suppose the same row shows the clue C on its right side. Reading from the right, the first filled cell must be a C. Together those two clues squeeze the A toward the left end and the C toward the right end, and the middle arrangement quickly follows from the one-of-each rule. Layer a couple of column clues on top and cells that seemed wide open suddenly have only one letter that fits. Watch how a clue and a blank interact: if the left clue is B but the leftmost cell is forced empty by a column above, the B simply slides one cell inward and every earlier deduction still holds. Learning to read a clue as the first letter after any number of blanks is the mental shift that makes the whole puzzle click.

Beginner tactics

• Remember that blanks are legal buffers. A letter can be pushed inward by empty cells, so the edge clue rarely fixes the very first cell.
• Read opposite clues together. Matching hints on the two ends of a line constrain both directions at once.
• Use the Latin rule constantly. Since each letter appears once per row and column, placing one letter erases options elsewhere.
• Corners are powerful. A corner cell answers to both a row clue and a column clue, so it is often the first thing you can pin down.
• Track which letters a line still needs, exactly as you would in Sudoku, so you never lose sight of what is missing.
• Count the blanks per line. In a five-cell row that uses three letters there are exactly two empty cells, so once you locate them the letters drop into the spots that remain.

How Easy as ABC compares to Sudoku

Of all the puzzles in this series, Easy as ABC is the closest relative of Sudoku, because at heart it is a Latin square where each symbol appears once per row and once per column. Strip away the border clues and you are basically solving a small Sudoku without the 3x3 boxes. What Easy as ABC adds is the visibility clue, the first-letter-seen rule that behaves a little like the sightlines in a Skyscrapers puzzle. Grasping what is Easy as ABC therefore feels natural to anyone who already thinks in terms of which value a row still lacks. The visibility twist then rewards that same instinct in a new way, asking not only which letter is missing but which one announces itself first from the edge. Master that and you gain a fresh feel for ordering that plain Sudoku never exercises.

That overlap makes Easy as ABC a natural warmup for Sudoku lovers, and it makes Shapedoku an equally natural home base. Shapedoku keeps the full classic ruleset, with every row, column, and 3x3 box holding all nine values once, but those values are nine glowing shapes rather than digits or letters. The shapes carry both a form and a color, so the board stays readable for colorblind players and looks like a small cosmos rather than a spreadsheet. Give it a try at app.shapedoku.com, or download printable grids and a free solver from shapedoku.com.