In P2's Dev Commentary, "sp_a2_pull_the_rug" has a commentary node that spits out SSTV signals explaining how Valve created the Portal radio ARG ("commentary/com-arg.wav"). Somehow, nobody has posted clean scans of the SSTV images from this commentary node (the best quality scan of these available online right now is from a horrendously low bit-rate 2011 Youtube video), so I went ahead and remade all three slides from scratch. The font is wrong, but happy reading ^^ <3