Roboto-Sans

File: https://yes-but-no.com/Roboto-Sans/ (This is taken down now)

Some clues are given from the name of the challenge itself, in this case Robot(o-Sans). Secondly, when we load the page, it talks about a game and robots.

So, we add /robots.txt to the back of the link to make it https://yes-but-no.com/Roboto-Sans/robots.txt. We can see that there is a disallow.

If we replace /robots.txt with /wg3cd.html, to form https://yes-but-no.com/Roboto-Sans/wg3cd.html we see the flag,

Flag: YBN{R0B0T5_4R3_Cøøl}