// THE CHALLENGE

Find an answer string such that:

sha256( "7977376013ed59ca469b9abd281b7afd" + answer )

has at least 16 leading zero bits. Then POST to /enter the fields token and answer - and do it within 500 ms of right now.

// machine-readable

nonce      = 7977376013ed59ca469b9abd281b7afd
difficulty = 16 bits
window_ms  = 500
token      = eyJrIjoiZ2F0ZSIsIm4iOiI3OTc3Mzc2MDEzZWQ1OWNhNDY5YjlhYmQyODFiN2FmZCIsImQiOjE2LCJ0IjoxNzg1MjUzMTk0MzE3fQ.612e5dd793b4dd958ce0c73c1062ee31b1f87c8e6b2eb1e97bc69a3070815c30

These values are also in the response headers (X-Challenge-*). Reading them is your job; computing the answer is your nature.