Friday, July 24, 2026

Sudoku Variant 4: Corner Sum (Addition Sudoku)

➕ Addition Sudoku — Corner Sum Challenge

How to Play:
1. Standard Sudoku rules apply: Fill digits 1–9. Every row, column, and 3×3 box must contain each digit exactly once.
2. Corner Sum Clues: The small red number at each grid intersection equals the sum of the four cells that meet at that corner.
3. All four cells around a clue are always distinct digits — so every clue value falls between 10 (1+2+3+4) and 30 (6+7+8+9).
4. Real-time hints: wrong digits turn red; completed rows/columns/boxes glow pale gold.

Tired of regular Sudoku and looking for something that truly stretches your brain? Meet Addition Sudoku — also known as Corner Sum Sudoku — an ingenious variant you may never have tried before.

At first glance the grid looks familiar. But those small red numbers scattered at the grid intersections are not decorations — they are secret clues holding the key to the entire puzzle.

🧠 How Addition Sudoku Works

1. Classic rules still apply. Fill digits 1–9. Every row, column, and thick-bordered 3×3 box must contain 1 through 9 with no repeats.

2. Read the red corner clues. Each number sits where four cells meet — it equals the sum of those four digits.

3. The four cells are always distinct. That means every clue falls between 10 (1+2+3+4) and 30 (6+7+8+9). This tiny constraint unlocks shortcuts you won't find in standard Sudoku.

4. Real-time hints built in. Wrong digits turn red instantly. Completed rows, columns and boxes glow pale gold so you always know your progress.

Why This Variant Is So Addictive

You can't just rely on row-and-box elimination anymore. Every move requires cross-referencing cells against their neighboring sum constraints:

  • Low clues (10–14) → force small digits nearby, locking out 7, 8, 9
  • High clues (26–30) → demand large digits, eliminating 1, 2, 3
  • Mid-range clues (18–22) → require balanced combinations — the hardest to crack

Every guess ripples across the board. One wrong placement and a corner sum breaks two rows away — you will learn to think three steps ahead.

If you enjoy Killer Sudoku, Arrow Sudoku, or Thermometer puzzles, you'll instantly fall for Addition Sudoku. It has that same satisfying "candidate crunching" feeling, but with a clean, elegant twist all its own.

Ready? Click any empty cell, tap a digit on the number pad, and start cracking those sums!


Share this challenge with your friends!Two brains are better than one!

Tags: addition sudoku, corner sum sudoku, sum sudoku, sudoku variants, free sudoku, daily sudoku

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