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2020-05-26 18:34 Arno  
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Now it’s the butterflies’ turn to show us their rolling skills! :-D  
  
There are, however, some surprises:  
  
\ The base-4 formation is possible. this is a mirrored counterpart of the firefly formation rolling-f4. But... a similar formation with 5, 6, 7 or 8 bflies is not possible. The corresponding ffly formations contain on a move relying on the cave scanning order, which excludes the possibility for a mirrored pair.  
  
\ The formation with 9 bflies, with complete left-most column, is again possible! :-) From then on, adding any number of additional bfly is possible and each formation mirrors its counterpart for fflies.  
  
\ Exchanging the bflies in the center for fflies is not possible. Such exchange is only possible for the firefly formations. This is because the top row is fully scanned first, so the inner flies are always blocked by the top row. On the contrary, fflies in the center of a bfly rolling formation would leave the formation via the left column since it contain gaps during a cave scan which happens row by row.

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2020-05-26 18:46 shredder  
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great! :) finally the bflies had thier parade! :)

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2020-05-26 18:48 DarkStoorM  
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Damn! Is it possible to mix them with FFlies?

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2020-05-26 18:50 shredder  
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thanks to help fireflies it's possible to create (launch) formation.

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2020-05-26 18:57 shredder  
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sorry my brain is sleeping today.   
  
thanks to help of fireflies, it is possible to create a butterfly formation... maybe even formations.