Chapter 1: First sums
4×4 In progressSome sums can be made only one way, and a run with one empty cell left takes what is missing.
Chapter 2: Longer sums
5×5 Sign inLonger runs with only one set: 6 is 1 + 2 + 3, 24 is 7 + 8 + 9, 10 is 1 + 2 + 3 + 4.
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Chapter 3: Where runs cross
6×6 Sign inWhere an across run meets a down run, a cell keeps only digits both can use.
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Chapter 4: Too big, too small
6×6 Sign inA digit is out when the rest of its run could not make up the sum.
Unlocks Medium in free play
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Chapter 5: Rule out sets
8×8 Sign inCross out the sets a run can no longer make.
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Chapter 6: Locked pairs
8×8 Sign inTwo cells that can only hold the same two digits use them up.
Unlocks Hard in free play
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Chapter 7: Must be in the run
8×8 Sign inA digit every set needs goes in the only cell that can take it.
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Chapter 8: Every way it fits
10×10 Sign inTry every way to fill a run; a digit in none of them leaves its cell.
Unlocks Expert in free play
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Chapter 9: Area totals
10×10 Sign inAdd up the clues around an area to find the cell that sticks out.
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Chapter 10: Master sums
10×10 Sign inEverything so far, on the biggest boards.