Star Battle: US Puzzle Championship 2019

[@Wecoc1]

17:29 Column 2 is forced in that point: r5c2 is a star, therefore r7c2 and r9c3 are also stars.

[@JFeingoldlink]

I would LOVE to have more Star Battle puzzles. They are just so much fun.

[@dekrachtbron-be]

The are star battle puzzles online at www.tectonicpuzzel.eu/star-battle-puzzle-online.html

[@dannyb.931]

17:29, there are 3 available adjacent spaces in the second column. The two ends must both be stars. There's your quick way :)

[@57thorns]

There can be a star in row 1 or 3 (c2), as well as 1 or 2 in c2 r5-r7, i cannot see how those are forced. I did get a few more constraints before I was essentially at the same spot.

[@LazerWulf]

@@57thorns At 15:30 he breaks that logic, showing that there can't be stars in r3c2 because all the stars in r3 have to be in that one shape, and at 15:52 shows there can't be one r1c2 because there must be one in r1-2c1.

[@LazerWulf]

17:29 As others have noticed, the only places in c2 for 2 stars are r5c2 and r7c2, and chaining those gets you stars in r9c3, r6c6, r5c8, and r7c4. r4c4-6 must have 1 star. There must be at least one star in r3c6-8, ruling out a star in r2c7. Those are the givens at this point. If you assume a star in r3c3-4, then there can't be a star in r2c3 or r4c4, meaning the 2 stars in r1 are in r1c3-4 and r1c7-8, meaning there must be a star in r2c1 and r2c5-6. If you put a star in r2c5, that forces 3 stars into c3, and the same thing happens if you put a star in r2c6 with c8. Since there cannot be a star in r2c5-6 with this logic, then the first assumption that there is a star in r3c3-4 cannot be true, meaning the stars in r3 are in r3c6 and r3c8, as you assumed, and the rest of the puzzle collapses.

[@philippwei3352]

A way without guessing at 13:20: You can cover the two regions of cells r3c4 and r4c4 with four 2x2-squares, therefore each of these 4 squares must contain exactly one star. If you look at the 2x2-square r34c34 and at column 3, you get some progress like this: start with a star in r2c4 -> star in r5c3 -> the square r34c34 is broken. Thus no star in r2c4, and from that you can get the empty cell at r2c8, and then proceed as you did. (Of course, the boundary between guessing and an involved chain of logic is fluent, my definition of guessing is whether I can do it in my head :P)

[@boskayer]

Man did i have trouble decyphering your notationand phrashing , but thanks!

[@philippwei3352]

@@boskayer I edited some stuff, I guess I wanted a bit too much to keep the description short. :) I actually dislike the "r3c4" notation: a chess notation (d3) would only be half as long and at least to chess players, it is really intuitive.

[@Nickle314]

17:30. Col2, Rows 5,6,7. That resolves quickly. You need 2 stars, there are two regions, they can't touch, so must be the top and bottom ones

[@57thorns]

What about row 1 and row 3, either of those are still possible.

[@Nickle314]

@@57thorns You need two stars in column 2. One in the blue area, one in the orange. They can't touch. So it has to be (2,5) and (2,7)

[@lukri8033]

At ~17:20 c2 needs two stars that means r5c2 is a star => r7c2 is a star => r9c3 is a star => there is a star in either r8c6 or r8c7 => star in r6c6 + r7c4 => star in r5c8

[@Pyromonkey83]

25 minutes, but a good 15 of it was staring at the grid with no progress beyond the same "T" logic you showcased. I had a little bit of help with this one, as I've seen a puzzle before that had very similar logic with the T shaped areas, which is the only reason I looked at it first. I ultimately ended up going for bifurcation as I couldn't spot the logic required, and got it wrong twice before stumbling upon the solution. The bottom 3 rows and the top 3 rows are keys to the solve, and where I focused the majority of my time searching for clues.

[@TevsTV]

A question I've had for a while but thought I'd put here since the video starts with a bit of discussion around bifurication: What's the actual difference between bifurication and trying to solve something by identifying a chain? Surely both are the solver picking a functionally random number and following it to see if it breaks. What makes one an acceptable piece of logic and the other not?

[@HeroDarkStorn]

The maid difference is, with bifurcation, if your guess leads to solution, you accept it and don't care how other guesses would end. With logic chain, you are not satisfied with chains that solve, you want logic chains that break. There is more of a sense of understanding why it is/isn't a solution, and it proves your solution is only one. You are right however, logic chain is inferior to "real" logic, and only arguably superior to bifurcation.

[@annacovici1504]

@@HeroDarkStorn that helps!

[@RoderickEtheria]

Labeling areas when they are considerably constricted already with a 1 and a 2 can be effective to get a few more insights, as around 13:39 you could have worked out that 2nd row, 6th column couldn't be a star, and you failed to notice this fact for a considerable time. With the shape in the bottom corner, you can immediately note that (7,7) could never be a star, as one of the stars in that shape is immediately forced into two locations connected on the sides of (7,7).

[@marklindsey1995]

If you make the grid a 5x5 chess board (of 2x2 blocks), each row and column must contain 4 blocks that have stars, and 1 that does not. The blocks without stars cannot see each other. In this puzzle those blocks are r1 b5, r2 b1, r3 b2, r4 b3, and r5 b4. In each row/column exactly 2 blocks will have stars in the top half, and the other 2 will have stars in the bottom. Similarly 2 blocks have left side stars, the other 2 right side stars.

[@joakimglimsjo1229]

13:20 I'm looking at cells r2c8 + r5c2, and the effect they have on rows 1-2, columns 1-2 and the upper left corner. If none of them are stars, the upper left corner 2x2 would have to contain 2 stars. If on the other hand both of them are stars, the upper left corner area can only contain a single star in r1c1 to complete both row 1 and column 1. Therefore, exactly one of r2c8 and r5c2 must be a star! If r2c8 is the star, then r1c6 -> r2c4 -> r3c6 -> r4c4 must be stars, breaking the T-shaped area marked in blue, so it must be r5c2.

[@jupitermonkey5687]

It took my dumb ass 5 minutes to understand the logic behind 11:08 and I thought I could keep going but now with 12:15 I'm just scratching my head endlessly.

[@mydemon]

Star battles are criminally underrated :)

[@tomcollyer641]

Lovely puzzle, and lovely logic! I have another suggestion for the online solver, which I don't think is very clear for the video. You need to maximise the ratio between minor gridlines and major gridlines if you want to be able to show the regions more clearly. I'd suggest (a) making the minor gridlines thinner, and also perhaps (b) making the major gridlines thicker (although not too thick!). You'll be amazed by the difference it makes.

[@MrCJHamill]

Thanks very much for this video! What are the other staple pencil-and-paper puzzles like Sudoku and Star Battle are there would you say? What are the absolute 'essentials' of these types of puzzles?

[@jumpiestudios5265]

Somehow this still feels way easier than the one I'm currently struggling with.

[@ebutuoyjg]

haha, same. I keep watching a video trying to find a hint that will help. im stuck

[@filam7371]

Star battles are hard for me to watch because of my colorblindness 😂 After a while it starts giving me a headache...especially since he's kinda forced to put blue and purple together or red and green together. And is there brown? He put a color next to green I absolutely couldn't tell apart from the green so I assume it was brown... I'd love to do these, but I'd have to use different colors OR use symbols/numbers to indicate the different cells.

[@hom-sha-bom]

If you want to *do* star battle puzzles instead of *watch* them, puzzle-star-battle.com is colorblind-friendly, using x's and star symbols instead of colors.

[@batdowg]

8:21 Fun puzzle! From 6:40 I went a different route which actually gave a lot more. Once you see the top of the T has to have a star, I checked if R2C8 could be a star. It forces R2C4, which forces R3C6, which forces R4C4, Which forces R5C2. That breaks column 1 and 2. No star in R2C8 mean Top T is only in row 3, Row 1 and 2 now restricted, forces Column 10, and just flows from there.

[@jonasgleim7612]

I don't think there is a simpler way than to test R2C8 like you did. The only other cells I found were R2C7, which is empty because of Col8, and a star in R7C45, which you get by looking at R78 simultaneously and dividing them into 2x2 regions. None of this helps, unfortunately :D

[@carsonwood1513]

Great job! I hit bifurcation a lot earlier. Would you be willing to try some of the word puzzles from the USPC? I am able to work through the ones like these (even if it takes me bifurcation) but some of the ones with placing words in the grid I can’t even start. Any advice?

[@Sianistic]

It's perhaps not a whole lot of help at 13:20 but R3C5 can't be a star since that'll interact with the shape below it, leaving it unable to fit two stars

[@Tehom1]

Beautiful puzzle.

[@mattjazzml]

Is this the same as parks puzzle? There you have trees instead of stars but the rules appear to be the same. Easier puzzles have only one star/tree. Great video! More of these please!

[@shane8037]

Yeah these are fun more of them

[@jeanbarque9918]

13:14 I don't know if it can help but since you elimiate the r3c5 option, r2c7 cannot be a star anymore because we need 2 in the J shape

[@ChristopherGermain]

16:42 A method for this position. Looking at the puzzle you have now, you know that r2c7 must be green, as no matter where you put the star in the J shape, you will end up blocking that position. C2 is also solvable.

[@Kuraudo_VII]

At 18:00 isn't the second column from the first obvious since it only has 3 possible place for 2 stars in a consecutive 3 cell?

[@josephrion3514]

Sixteen and a half minutes in I am looking at column two for where to put two stars in only three adjacent spaces.

[@notchmath9642]

I tried this and about all I could find was that there wasn’t a star in the fourth row down third column left (above the T-shape). I realized that either the stars in the T-shape were both in the vertical line or they weren’t. If they were, then the column would be full and we couldn’t have a star in the box above it. If they weren’t, then there was a star in the lips touching that box so we still couldn’t have one there. Also certain obvious things like the box in the lower right not having one in the middle spot

[@mhelvens]

13:20 At this point I concluded r5c1 couldn't be a star, because it would break the r4c6 shape. From there, I could separate that shape into regions of 2 and 3 cells that would need to contain stars.

[@jeanbarque9918]

Why would it break it? R4c5 and r4c7 can still be stars

[@TheR0ry]

Where can I view all of the puzzles from the US puzzle championship?

[@shane8037]

ESPN8, the Ocho.

[@ElyotGrant]

On the site: wpc.puzzles.com/uspc2019/download.asp

[@leporid257]

Oh different background

[@johnydl]

at 13:21 I spotted some nice logic on row 1 and 2 way way earlier in the puzzle that gave me progress that you'd be able to actually utilise a lot here the top 2 rows have 4 2x4 boxes to put stars in I was closer to 6:40 when I spotted that and I used a chain to look at r2c8 is it a star? if r2c8 is a star r2c4 must be a star to have 2 stars in its box and so r1c6 and r3c6 must both star as the only spaces left in thier boxes and r4c4 must be a star to allow its box to have 2 stars because of this we reach a contradiction with your 7:38 logic a star can't go in r5c2 cause of the constraints on the other boxes in c1 and c2 and r4c4 limits r5c3 and r5c4 A star, therefore, mustn't go in r2c8 2 stars must go in r3c3 to r3c8 so r3c10 is not a star and r4c10 is A star cannot go in r2c4 or 3 star's in that box A star must go in r5c2 or there's not enough stars in c1 and c2 this would give you r7c2 as a star which in turn gives r9c3 A star must go in r5c7 or r5c8 and A star must go in r8c6 or r8c7 putting a star in r6c6 and from here the puzzle is largely complete Which is what you seemed to do up to 17:32 except you failed to spot the r5c2 deduction that it has to be a star for there to be two stars in it's column

[@tomelipanda]

11:08 if a box have a star. IF

[@leppyr64]

13:20 R7C4 or R7C5 mist be a star when paired with R8. That let's you fill R6C4 and R6C5.

[@TheMaRkT123]

12:30 isnt that logic wrong? You can fit 3 stars in the region so its not true that the one from last column must be star? Someone explain pls

[@Soulavenger69]

He has to put 4 stars in the two rows he was highlighting (r6 and r7), and he could only put 2 in the middle region of those rows, that forced the remaining two stars for those rows in the left and right ends where he indicated earlier there must be stars in order to complete the rows, which forced r6c9 into being a star.

[@carstenkruse8527]

@16:45 c2 needs two stars. Therefore r5 and r7 has to be the stars

[@Endominateur]

why cant it be one and three or a mix of any of those?

[@cherrim3881]

my brain explode

[@andrewgrant6516]

Column 2 was solvable long before you pushed a star into it as a result of guessing.

[@mattovell]

This is a great puzzle type! But how would you go about solving it on paper, say if it was in a newspaper, without having lots of different coloured pens? Maybe that's why it isn't as popular as sudoku

[@draconicdusk5911]

18:00 there is actually a way to solve this without assuming that R3C6 and R3C8 are stars. It's a lengthy explanation, so I put it in an email with screenshots.

[@kamikazegargoyle]

Did it in 1 hour 07 and i don't know how to do it without brute force bifurcation, maybe i'll watch the video to find out but it's the middle of the night *cry*

[@leethielemier8592]

But there isn't a unique solution.. from the finished solution, move the star from r1c5 to r1c4, move the star from r2c3 to r3c3, move the star from r3c6 to r2c6, and move r4c4 to r4c5. This would be another correct solution. Since there isn't a unique solution, there would be no way to logically solve the puzzle without bifurcation..?

[@spiff256]

The star you move to r2c6 would be diagonal to the star in r1c7

[@BryanLeeWilliams]

I didn't like this one because you had had to guess toward the end. I like logical conclusions.

[@draconicdusk5911]

It does have a logical conclusion though. Column 2 is forced and if you follow the stars that are made that way you will come across what looks like another guessing point. However, some beautiful logic using what I'm calling Battle Star's version of an X wing, eliminates a possibility on R2C6 and then you can eliminate R3C4 using the logic that it's always seen in any circumstance. Afterwards R3C3 and be eliminated cause it will cause a contradiction and from there the puzzle cracks wide open.

[@ashishkumar-tz9ii]

Hi. Do let me know where you had to guess.. will help you with the logic.

[@BryanLeeWilliams]

@@ashishkumar-tz9ii i don't understand why he put a star in row 2 column 8. It seems that was just a guess and i couldn't figure out a logical reason for it.

[@ashishkumar-tz9ii]

@@BryanLeeWilliams you mean Row 3 column 8? I do not see any star at Row 2 column 8. Exactly at what time of th video you need the logic to proceed

[@BryanLeeWilliams]

@@ashishkumar-tz9ii oh yes i think row 3 column 8