they tell you right on the page to try inspecting
out of curiousity, I also checked the source.  there is a comment telling you it won't be that easy and sending you to a rickroll youtube link (https://imaginaryctf.org/r/69696969)
there is also a script with some obfuscated bullshit that probably prints something
so I went to the inspect panel and checked the debug console
and yeah, there it was