We were wondering if this new craze of flip sequins is a problem on Shabbos/Yom Tov.
We have a pillow that you can really draw/write things in because of the way the flip sequins work.
Is this considered writing from a halachic point of view?
Yes it would be halachically considered writing. The reason being, that the picture that is made on it will remain that way, at least temporarily, which would be kosaiv m’drabonon. Therefore to write letters, a picture or even a shape that has meaning to it would not be permitted on Shabbos or Yom Tov. Regarding making squiggles etc. that are meaningless, technically it would be permitted, but it is not recommended, because one might inadvertently write something that has meaning to it, therefore it is best not to play with it on shabbos.
M:B 340- 20, 25(1), Biur Haacha D:H B’mashkin, Zachor Vshamor (Kosaiv) pg. 4, R’ Y. Cahen shlit”a.