What about Vala [0]? Its systax is similar to Java or C# but is almost as
efficient as C.
Vala is the language chosen by elementary [1] to develop their applications
and GNOME games are being ported to it as well.
Glade [2] is another option for UI design, if you prefer GTK+ instead of Qt.
[0] https://wiki.gnome.org/Projects/Vala
https://wiki.gnome.org/Projects/Vala/Documentation
[1] http://elementaryos.org/journal/why-we-write-elementary-apps-in-vala
http://elementaryos.org/docs/code
[2] https://glade.gnome.org/
