Good job! I really liked this one, especially the artstyle and the carcasonne-like gameplay, but it seems to get a bit monotone after a while. I think it would be nice to have a second slot for another puzzle piece so you would have more opportunities. Or maybe a crate that gives you a needed tile or lets you remove an unwanted tile. Another thing I would like to see is a reward (f.e. in points) for filling the plane so the motivation is higher to not just build to the boxes (a limited view range could help here as well). All in all I just can say: Nice Work!
Edit: It would also be nice to have a button which shows the current reachable places. Currently I'm sometimes not sure if a box is connected or not. Thanks again for building this game, I'm really having fun here^^