DUSK is a truly awesome retro shooter, and one of the main reasons why the genre is having such a resurgence these days. But if that alone simply isn't enough, DUSK has just become even better through the addition of official modding support!
The whole system is still in alpha so it's not fully fleshed out just yet, but there are already quite a few mods available to toy around with. As you might expect, most are currently just texture or audio replacements, though there are a surprising number of community-made levels as well. You can check them out over at the DUSK modding website.
As for the future, the DUSK team has a whole bunch of new features coming for the modding tools. Once implemented, the community will be able to create custom models, introduce new enemies and weapons, use scripting to create their very own events, as well as upload and share their mods with the world through the Steam Workshop. Perhaps most interestingly of all, the developers are eventually planning to make DUSK entirely open source, which could lead to some rather interesting spin-offs.
So if you're a fan of oldschool shooters and you still haven't given DUSK a try, this would be a pretty good time to jump on the bandwagon. Have fun, and you can learn more about the modding tools over at Steam.