I noticed that there are no 64-bit deb packages available for download, but it's rather trivial to repackage the 32-bit deb to work on a 64-bit system. All you need is a patch for the control file:

--- old/control 2009-02-10 16:38:14.000000000 -0600<br />+++ new/control 2009-03-13 18:29:44.000000000 -0500<br />@@ -1,11 +1,11 @@<br /> Package: WorldOfGoo<br />-Architecture: i386<br />+Architecture: amd64<br /> Version: 1.40<br /> Maintainer: Maks Verver <maksverver@geocities.com><br /> Section: games<br /> Priority: extra<br /> Homepage: http://www.worldofgoo.com/<br />-Depends: libc6, libstdc++6, libgl1, libglu1, libx11-6<br />+Depends: libc6-i386, lib32stdc++6, ia32-libs<br /> Installed-Size: 75016<br /> Description: A physics based puzzle/construction game<br />  The millions of Goo Balls who live in the beautiful World of Goo don't know<br />

Works fine under Ubuntu 8.04 with all dependencies met. This would save some frustration with 64-bit users.

Yes, this works. I posted a script to repackage the 32-bit package as a 64-bit package in this topic a while ago, which takes care of the unpacking/patching control file/repacking stuff.

(The reason this 64-bit package isn't released officially is that it still contains 32-bit executables with dependencies on 32-bit libraries, so if we'd release it like this people would still be complaining that it isn't a "true" 64-bit package.)