I wrote an ebuild for this really addictive game. Here it is.
Created attachment 84799 [details] watermelons-1.1.1.ebuild
Created attachment 84819 [details] watermelons-1.1.1-r1.ebuild
Couple issues: The source needs to be patched to write to GAMES_STATEDIR instead of GAMES_DATADIR. Writing to the data directory isn't allowed. The tarball needs a version. Putting an unversioned tarball on the mirrors isn't allowed. Also, creating the wrapper should be done in src_unpack rather then src_install.
Created attachment 84847 [details] watermelons-1.1.1-r2.ebuild New revision, according to Mr. Bones' advices. About version in tarball name, I'll try to tell upstream.
Created attachment 84848 [details, diff] files/watermelons-statedir.patch
Created attachment 84878 [details] watermelons-1.1.1-r3.ebuild
In portage. When attaching ebuilds in the future, leave off the -r#. That's for rev bumps in portage, not in bugzilla.