So I've just started practicing look ahead during F2L more seriously, and I have a question regarding corner deduction. In theory, it's possible to deduce the corners in the front slots without looking at the bottom of the cube. Is that something most top cubers do or are they sometimes tilting the cube slightly to see the bottom? I'm guessing it's the former since it doesn't seem too hard to master with enough practice (even I can already do it, but I can't always do it fast enough).
Deducing front corners during F2L
- Thread starter Aergyl
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Technically you can deduce it like that, but IMO it's easier to compare the corner colors relative to the adjacent cross/center pieces. Just like with 2-side PLL recognition, you look at slightly more stickers than needed but you get a very nice pattern that's easy to recognize. I'm curious about how other people recognize it though!
Of course, sometimes you can easily deduce the front slot corners by process of elimination, but I'm just wondering if there are people that deduce them without extra information. For example, I do it subconsiously for easy cases like a solved corner (i.e. when both colors matches with the adjacent cross edges), but I can't do it without active thinking for all cases yet.
Please let me know how you/others recognize/deduce front slot corners
Please let me know how you/others recognize/deduce front slot corners
For anyone interested, I'll explain in more detail how I deduce the front corners without looking at the bottom. For the sake of simplicity, I'm going to assume that the cross color is white, but the same concept can be applied to any cross color.
First of all, I can sometimes deduce which corner it is by process of elimination. The idea is to use any information about what you currently see/remember about certain pieces to eliminate the other possibility. This is very useful and easy to do when a lot of F2L is already solved, but can sometimes be used earlier as well.
However, sometimes it's easier to deduce the corners by looking at the color pattern formed by the corner and its adjacent cross edges. In other words, the pattern consists of 4 colors in a row. There are three different cases that I will explain separately.
1. Yellow is visible. In this case, we simply ignore it since knowing which yellow corner it is is completely useless information most of the time.
2. White is visible. In this case, we immediately know it's a corner we care about, and we want to know where it belongs. If there are matching colors with white between, the corner is in its own slot. If there are matching colors next to each other, it's in the adjacent slot with that color instead. If there are opposite colors with white between, the corner is in the diagonally opposite slot. And there's only one possibility left for when there are opposite colors next to each other.
3. No white/yellow is visible. In this case, we simply want to know if it's a yellow corner we can ignore or a white corner we care about. If there are two matching colors, the corner is white if they are next to each other and yellow if they form a checkerboard pattern. If there's only one matching color, it's yellow if they're next to each other and white otherwise. And when there are no matching colors, the corner is white if there are two opposite colors next to each other.
Theoretically, it's even possible to deduce the corners without using any other information than the two visible colors, but I personally find that harder to do. I'm very curious about what other people use though! I'm also grateful for any thoughts/questions etc. about the method I'm using
First of all, I can sometimes deduce which corner it is by process of elimination. The idea is to use any information about what you currently see/remember about certain pieces to eliminate the other possibility. This is very useful and easy to do when a lot of F2L is already solved, but can sometimes be used earlier as well.
However, sometimes it's easier to deduce the corners by looking at the color pattern formed by the corner and its adjacent cross edges. In other words, the pattern consists of 4 colors in a row. There are three different cases that I will explain separately.
1. Yellow is visible. In this case, we simply ignore it since knowing which yellow corner it is is completely useless information most of the time.
2. White is visible. In this case, we immediately know it's a corner we care about, and we want to know where it belongs. If there are matching colors with white between, the corner is in its own slot. If there are matching colors next to each other, it's in the adjacent slot with that color instead. If there are opposite colors with white between, the corner is in the diagonally opposite slot. And there's only one possibility left for when there are opposite colors next to each other.
3. No white/yellow is visible. In this case, we simply want to know if it's a yellow corner we can ignore or a white corner we care about. If there are two matching colors, the corner is white if they are next to each other and yellow if they form a checkerboard pattern. If there's only one matching color, it's yellow if they're next to each other and white otherwise. And when there are no matching colors, the corner is white if there are two opposite colors next to each other.
Theoretically, it's even possible to deduce the corners without using any other information than the two visible colors, but I personally find that harder to do. I'm very curious about what other people use though! I'm also grateful for any thoughts/questions etc. about the method I'm using
Wow, how did I miss that for so long? Never been aware you can deduce corners with two stickers. Makes me wonder what else I missed about look ahead. More deducing stuff?
Jperm has a lot of nice videos about look ahead, and this one is specifically about deducing pieces in the back slots:
I also forgot to mention another useful technique, where you deduce a front slot corner relative to the edge in the same slot. The idea is to visually see if it makes sense for them to be a connected F2L pair or not. If we ignore the obvious cases where the corner has colors that can't possibly belong to that F2L pair, there are four different patterns:
This might sound a bit complicated, but with practice I'm pretty sure it can become very easy to tell intuitively without any active thinking that it "looks correct" or "looks wrong". Please let me know what you think about this tecnique!
- Both of the edge colors matches with the corner, and the matching colors are next to each other.
- Both of the edge colors matches with the corner, and the matching colors are diagonally opposite.
- Only one of the edge colors matches with the corner, and they're next to each other.
- Only one of the edge colors matches with the corner, and they're diagonally opposite.
This might sound a bit complicated, but with practice I'm pretty sure it can become very easy to tell intuitively without any active thinking that it "looks correct" or "looks wrong". Please let me know what you think about this tecnique!
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