I started doing PicoCTF challenges yesterday (essentially the gamification of learning various cybersecurity topics like binary exploitation and reverse engineering), and it's pretty fun! I learned what Capture-The-Flag's were because of Cybersecurity Club last semester, but I never participated in any of the large-scale ones that club members and executive board members played in on weekends -- despite the fact that I was taking a reverse engineering and vulnerability analysis course at the time (CS 390R).
The challenges (I've done 30 at the time of writing this) so far deal with general Linux skills and reverse engineering, so I've opened up Ghidra a few times to solve some things and look at stuff like the eax register. Otherwise though, after following their "Low Level Binary Intro" playlist which consisted of basic stuff like converting hexadecimal to ASCII, etc, I think it's a pretty fun way to keep my skills (relatively) sharp over the summer. I spent almost three hours straight doing problems last night and accrued over 2,000 points!!
I followed the PicoCTF Primer a little bit in the beginning, although redundant when compared to CS 390R's teaching introduction for the most part, but I had a lot of fun! If you are interested in reading the 390R material from last semester, it is all posted on the Cybersecurity Club's front-facing website dedicated to 390R: pwn.umasscybersec.org. It covers topics ranging from Assembly to stack and heap exploitation to automated program analysis (i.e. fuzzing). Shoutout to Steven and Gilbert for teaching this course last semester!