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# Puzzle 40b
- URL: https://www.workroom-productions.com/puzzle-040b/
- Published: 2026-08-08T15:59:46.000Z
- Updated: 2026-08-08T21:36:57.000Z
- Description: Variant of Puzzle 40. Spot the difference?
- Author: James Lyndsay
- Tags: Puzzle

Describe how the buttons affect the lamps. 

This version has a single meaningful change from [Puzzle 40](https://www.workroom-productions.com/puzzle-040/) – you could use [diff](https://www.workroom-productions.com/diff-for-testers/) to find it, you could look at the behaviours, you could think of somewhere I might easily have dropped in a meaningful change that doesn't quite get picked up by typical validation tests. You could ask, of course. 

I don't typically put bugs in. This change is intentional, so arguably it isn't a bug. But the behaviour it introduces does, in some sense, break the symmetry of what you might have found in 40\. Off we go then.

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