Hidden ball 3:

Solution

we check robots.txt and see the following message: We are people, not machines

so then we check people.txt: What's about akronyms?

so then we check humans.txt and see:

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All credits go to the following incredibly awesome HUMANS (in alphabetic order):
avarx
DanMcFly
HaRdLoCk
inik
Lukasz
M.
Morpheuz
MuffinX
PS
pyth0n33

HV17-bz7q-zrfD-XnGz-fQos-wr2A

whoo, theres a flag!

Flag