the actual tunnel itself is quite passable @ 1680x1050. what detracts from the quality, to me, is the "furthest reaches" or distant end of the tunnel (maybe the last 1/3).
could you blur, smooth or fade the "back" 1/3 of the tunnel somehow? that's where the blockiness is. the wall in the "closest" 1/2+ is quite nice but the back is distracting.
otherwise, the font resolution should be upped (and i wouldn't use red as a border).
still, "passble", in my book, as is. nice work
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