I'm a math student dealing with complexity theory for the first time.
I'm struggling with the following exercise, hope someone will help me!
I need to show that the following decision problem is NP-complete.
An instance of the problem, which is actually a smartphone game called InfinityLoop, consists in a rectangular grid in which each tile is one of the six ones in the image 
Each piece can be rotated by multiples of 90° (in place rotations).
Solving a given instance means that operating these kind of rotations you can find a configuration in which the limits of each piece are connected to the limits of its neighbor pieces (meaning that we can't have open lines). For example the (a) image is a solution of a given instance,(b) isn't:
The question of the problem is, of course: given an instance, can we solve it?
The problem is, of course, in the NP class, I need to show it is NP-hard.
It can be formulated as an edge matching puzzle (labeling the edges with 0 and 1) and I found a lot of literature about complexity of these kind of puzzles but I didn't manage to find a clear way to show the thesis. I tried to emulate the strategy proposed for the much more complicated but similar problem solved in this article about Tantrix game https://pdfs.semanticscholar.org/face/76a03fdb99f22b2630b07dfe7faea7359823.pdf?_ga=2.47860199.1507314508.1567418675-1855322905.1567418675, i.e, I tried to reduce the Boolean Circuit problem (which is NP) to my problem but I'm really new at these concepts and couldn't find a clear way to do so.
P.S. Also if not specified in the exercise I assumed that the given grid can be of any rectangular shape, otherwise I could just try all the possible 16^N configurations (being in this case N the constant number of the cells) making the problem P (right?)
Thank you!