Nice game! Though the mechanic of (ROT13) oyhr pbaqhpgvat terra (ROT13 end) is only required at the final puzzle and can be confusing. I looked at the other comments and you said an earlier puzzle should illustrate that, but it kinda didn't?
You're completely right, my attempt to fix the issue failed again : P now that ratings for ludum dare are over I can make another update. The idea is that you were supposed to be required to use the mechanic to complete (ROT13) gur ebbz jvgu bayl oyhr naq terra. Thank you for playing and for the feedback!