If they literally copied your website, this is a simple case of copyright infringement. Source code, descriptive text and graphics are each individually subject

If they literally copied your website, this is a simple case of copyright infringement. Source code, descriptive text and graphics are each individually subject to copyright. You should be able to file a DMCA request to remove the offending app. Assuming their app that copied yours was successful, a lawsuit for damages might be worthwhile. Note that the simple concept of a game is not subject to copyright. Also note that your failure to register does not relieve the offending party of liability though it might remain advantageous to do so. In short, talk with a lawyer. Disclaimer: I am not a lawyer and the foregoing should not be construed as legal advice.