
Show HN: Light Flip – A cell inversion puzzle game - rmal30
https://play.google.com/store/apps/details?id=com.rmal30.lightflip&hl=en
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mcphage
Why is this one different from the hundreds of similar clones?

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rmal30
Lights Out flips the neighbouring cells, this game flips all cells in the same
row or column

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wingerlang
You should probably make this really clear. I probably wouldn't download
either version, however without any clear difference from the other 1000s of
clones I instantly dismissed it after not seeing anything new.

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rmal30
Added a note

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bbcbasic
On even board to flip a square, hit square and hit all other squares in the
same row and all other squares in the same column.

To flip 4 squares in a 2 x 2 arrangement, hit all of those 4 squares.

What makes the bigger grids hard is the size of my little finger.

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vsviridov
This reminds me of a puzzle in an old point-and-click adventure with a Fridge
with a lock like this...

[http://questgame.ru/images/pilots/2.jpg](http://questgame.ru/images/pilots/2.jpg)

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nickcw
I had fun playing this game for a while. Eventually I discovered some fairly
reliable algorithms which enabled me to collect all the achievements. I'd like
some bigger boards to have a go with now!

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rmal30
Glad to hear that you're enjoying the game! I've added the 8x8 board. In the
average case, it can be solved in around 32 moves using the most optimal
algorithm.

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nickcw
Thanks :-)

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smcmurtry
I haven't downloaded the app, so maybe this makes sense somehow, but the
following text from the app description confused me:

Difficulty ratings:

\- 2x2 board - Easy

\- 3x3 board - Easy

\- 4x4 board - Hard

\- 5x5 board - Medium

\- 6x6 board - Impossible

\- 7x7 board - Hard

Shouldn't the difficulty rating increase with increasing board size?

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rjp0008
Solving an even square might be inherently harder than an odd square. I
haven't played the game though.

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rmal30
Yep, it requires n^2 moves for even boards while odd boards require less moves
(no formula found yet). Using a computer, I found, by brute force, that the
5x5 can be solved in 8 moves at most, the problem quickly becomes intractable
for 7x7 and above. It looks like this might be NP hard according to another
post: [http://stackoverflow.com/questions/27436275/how-can-i-
furthe...](http://stackoverflow.com/questions/27436275/how-can-i-further-
optimize-this-solver-of-a-variant-of-lights-out)

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fluffyllemon
Strategy that seems to be pretty effective: click all the squares that are
originally yellow

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vgddvh
Why would anyone play this game when he could just diagonalize (nxm)x(nxm)
matrix in F2 and get a basis? (in case of non-singular, otherwise impossible)
upd: misunderstood the game, it's about solving Ax=b in F2, so Gauss
elimination.

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nhebb
Yeah, that's what the rest of us were thinking as well.

