comes from Kishor Berde. Recently I blogged about Kishor's other game SARKWO. I liked it so much I thought I'd try his other game.
The first 20 levels were so easy and I wondered why I was still playing. But gradually, new elements were being added and things got more interesting.
The black squares with a marble: they're fixed.
The black squares with multiple colors (see the third image) can be rotated.
The connecting lines have their own button not attached: tap on it and the corresponding buttons will swap.
There are 170 levels and at the moment I've done 87 levels. I did these all on my phone while killing time.
Advice to all puzzle app developers: Don't publish more than 100 levels.