git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@1544 542714f4-19e9-0310-aa3c-eee0fc999fb1
horizontal/vertical. git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@1148 542714f4-19e9-0310-aa3c-eee0fc999fb1
we can interchange direction constants without requiring conversion and so that we only have to define this stuff once. git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@817 542714f4-19e9-0310-aa3c-eee0fc999fb1