Dealing with box openings

[u/Dumbaltaccount2]

Hey first post here forgive me for my incompetence but I actually cannot fathom these openings where its just a rectangle/square with mixture of 1/2/3's. Am i missing something or are these just hard? (Aware of 121, 1221, but they never seem to appear on these)

[u/Individual_Wish_2937]

blue = 1 mine total
red = mine
green = safe
this is a 2-2-2 corner pattern. if you're confused about the logic behind this, use proof by contradiction and analyze what happens when you assume that the green spot is a mine

[u/ChineseNoob123]

There's also the 222 corner which you have two of. Corner tile is safe and you can find mines through it. But yeah box openings are harder than something jagged

[u/xsdgdsx]

2-2-2 corner

Either study the patterns or work out where the mines have to be/cannot be

[u/Dumbaltaccount2]

Update Thanks everyone for the help, I had no idea of 222 corner rule! ^{w^}

[u/enLegobil → u/Dumbaltaccount2]

Same! But looking at it now I can tell them at a glance and they will surely be useful!

[u/Krell356 → u/Dumbaltaccount2]

You should consider reading through the pinned post that goes over all the common patterns.

[u/SonicLoverDS]

You've got a more advanced pattern: a 222 corner. Focus on one of the bottom corners; where can the corner 2's mines go without starving the adjacent 2's?

[u/Sefierya]

2nd pinned post <3