Didn't entertain me...
Sniper games are hard to make fun, and it's mostly the story that makes it. Although I was curious about the stone age reference (a shooter in those times?), having an archaeological background, I could only but be disturbed by the fact the character uses a crossbow... Stone age is ca 700.000 BC, and the earliest crossbow found dates from ca. 2.000-3.000 years ago.
Maybe if the story was actually animated and/or voice-acted it would've made it better though.