VolgaCTF 2017 Quals
Organizers did a great job with VolgaCTF Quals, you can tell that they have been doing this for several years. Things were very well set up and thought through, and most of it went without a hitch. Some of the online challenges were kind of slow, but the admins seemed to be responsive to requests for help and fixed challenges fairly quickly when they went down. I had a great time and learned a lot.
Here are some of the challenges that I solved: