Ask HN: Which design rights are enforceable in the United States?

Hey guys, I created a puzzle game as a side project a few years back. It's similar to a Rubik's Cube, but in 2D instead of 3D. Here's the Google Play listing: http://goo.gl/o7X6I An identical listing also appears in Amazon's and Barnes and Noble's stores. Yesterday, I received a takedown notice from Amazon that advised me to contact Rubik's Cube's security team. Their representative sent me this note: > (Y)our images of the cube is infringing our designrights. Please see attached certificate. You will have to change the design of your cube or get a license from Rubik's Cube. > Attachment: http://goo.gl/08Cq6 I'm based in the US and they are based in Sweden. My understanding of US IP law is that puzzle design is not protectable, and I was very careful not to call my puzzle a Rubik's Cube in its description. I don't know what the rules are in Europe. The name, design, and logo of Cognicube are distinctively mine. I don't believe the concept of sliding colored bricks to solve a puzzle is protectable in the US. The only thing I can see in their application that is even remotely similar to Cognicube is their logo. It's is an isometric projection of a Rubik's Cube from the corner. In the tablet version of Cognicube, there's a view that shows all six faces of the cube displayed in quasi-3D. It's not my logo, and it's drawn from a different angle than the image in their trademark. (It also has six faces instead of three.) Compare: - Their logo: http://goo.gl/oZd0C - My screenshot: http://goo.gl/3Stve I know that Hacker News is not an outlet for legal advice, but I imagine you guys may have run into similar issues before. Are EU design rights enforcable in the US? Do you see anything I've done that infringes their rights in the US? I've only made a couple hundred dollars over the last few years on this project, so it might not be worth contesting, but if I'm actually infringing something, I'd like to know for next time. =) Thanks!