Complete the puzzle SMPL in I/O STREAM section. This is four puzzles down and two puzzles to the left of the second puzzle we complete for achievements. Text solution:
DDDL LLDL SSSD UURU LLLL LLS
(U=Up, L=Left, R=Right, D=Down, S=Action)
Full achievement video walkthrough. This puzzle can be seen at 3:04: