Difference Engine
(Published on 30. June 2025, 18:36 by sshrpe)
I wanted to make a puzzle themed around computers, with a readout area that gave an output based on a number of input lines throughout the puzzle. Chatting with the lovely folk on the CtC Discord about it then led to the invention of Binary Sum Lines, which made their debut in this puzzle by RockyRoer, who also provided an excellent introduction and explanation for how they work, as well as a smaller example puzzle. Do check out Rocky's puzzle, it's really great!
RULES
- Normal sudoku rules apply. Fill the grid such that the digits 1-9 appear once in every row, column, and 3×3 box.
- Binary Lines: Green lines form a binary number along their length, where even digits represent 0s and odd digits represent 1s. The decimal value of the line is shown by the attached bulb, which reads from left to right. The 'most significant bit' is the cell closest to the bulb. For example, a line reading (from bulb to tip) 8-3-1-4-6-3 has a binary value of 011001, giving a decimal value of 25. Small numbers in cells on lines show the decimal value of their position along the line, for reference.
- Output Cages: Cages display the sum total of all the lines which enter them, as a decimal value read left to right.
I really hope you enjoy this puzzle. Leave a comment below to let me know how you get on!
Solution code: The sum of the two output cages, as a binary number
Comments
on 15. July 2025, 13:28 by damo_89
Another lovely binary sum instalment
on 1. July 2025, 02:58 by sanabas
Good to see people having ideas that cause inspiration in others too. :D
Also, great puzzle.
on 30. June 2025, 22:27 by vfig
neat puzzle!
getting to the end and having to do more maths for the solution code is a bummer.
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sshrpe: Sorry to hear you didn’t feel the same delight some others do when an unexpected opportunity for extra maths arises. Each to their own, I guess. :) Thanks for solving, glad you liked the puzzle!
on 30. June 2025, 21:36 by cryptique
Great puzzle, nice work
on 30. June 2025, 19:21 by RockyRoer
Very fun! I enjoyed the addition of some decimal number summing logic too! Sorry again for stealing your idea!
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sshrpe: Haha thanks! ‘Stealing’ here means ‘significantly improving’, and I’m very grateful! :-D
