2017-08 update.
Done:
Network: Looks good! Overtime is implemented, I'll look for minor bugs and improvements about overtime. Matt already played a session and reported no problems, this makes me happy. Large session
this Sunday, September 3rd. (Handicap and neutral lixes are long-term feature ideas, but not urgent.)
NepsterLix: Perfect. lemforum, NepsterLix, and Rubix's levels are 100 % solvable in Lix 0.8.
Tilesets: Great progress. Raymanni's 3 awesome tilesets and my renovation of Oriental ship with Lix 0.8. We have idling animations!

Large-scale issues:
Music: Still widely open, no music at all. Still
high demand.
Installability: Lix should be installable by standard Linux package management, and new Lix versions shouldn't clobber user data. Allow Linux Lix to read not only from its own directory, but also from, e.g.,
~/.local/share/lix and
/usr/local/games/lix. Similarly, is Windows Lix OK with reading only from its own dir, or start supporting
Users/AppData?
Tilesets: Only some redesigns that won't affect physics. I'm not happy with the lighting in matt/marble: Bevel effect leaves flat edges near top and left. Maybe improve the paper-cut-out look on matt/beach and matt/winter.
ClamLix: Unmaintained, doesn't ship with Lix. Clam has been absent for over a year. Feel free to pick it up, cover it with replays, and redesign the few levels that don't solve in D Lix. Humane replays are in the
replay database on github.