Most 2-digit BUG-light unavoidables are rather easy to spot, because you just can "extend" them with simple rules. E.g when you have this one in mindcoloin wrote:[I dont know how you can say they are easy to spot !

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`+----------+----------+`

| . 12 . | 12 . . |

| . . . | . . . |

| . 12 . | 12 . . |

+----------+----------+

- Code: Select all
`+----------+----------+`

| . 12 . | 12 . . |

| . . . | . . . |

| . 12 . | . . 12|

+----------+----------+

- Code: Select all
`+----------+----------+----------+`

| . 12 . | 12 . . | . . . |

| . . . | . . . | . . . |

| . 12 . | . . 12| . . . |

+----------+----------+----------+

| . . . | . . . | . . . |

| . . . | 12 . 12| . . . |

| . . . | . . . | . . . |

+----------+----------+----------+

- Code: Select all
`+----------+----------+----------+`

| . 12 . | 12 . . | . . . |

| . . . | . . . | . . . |

| . 12 . | . . 12| . . . |

+----------+----------+----------+

| . . . | 12 . . | 12 . . |

| . . . | . . 12| 12 . . |

| . . . | . . . | . . . |

+----------+----------+----------+

- Code: Select all
`+----------+----------+----------+`

| . 12 . | . 12 . | . . . |

| . 12 . | . . . | . 12 . |

| . . . | . 12 . | . 12 . |

+----------+----------+----------+

Also with 3 digits and pairs of candidates (i.e 2 possible solutions) some extensions are easy, when you have this pattern in mind:

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`+----------+----------+----------+`

| . 12 . | . 23 . | . 13 . |

| . . . | . . . | . . . |

| . 12 . | . 23 . | . 13 . |

+----------+----------+----------+

Here e.g. instead of the middle pair you can have

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`+----------+----------+----------+`

| . . . | 12 . 12| . . . |

| . . . | . . . | . . . |

| . . . | . . . | . . . |

+----------+----------+----------+

| . 12 . | 23 . . | . 13 . |

| . . . | . . . | . . . |

| . 12 . | . . 23| . 13 . |

+----------+----------+----------+

| . . . | . . . | . . . |

| . . . | 13 . 13| . . . |

| . . . | . . . | . . . |

+----------+----------+----------+

- Code: Select all
`-----------`

1..|2..|3..

.2.|3..|1..

...|...|...

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21.|

...|

...|

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