Well, I have the Loop Dog achievement (which I think you can see the description for normally?) and my interpretation was that it just means to "complete" the game until it loops back to the first world's background color. Of course, when that happens (the first time, at least) is when you start racing the blue saw blade. Since the graphic for Double Dog has 9-1 in it, I assume that it's when you reach the level count of 9-1 which would be the total of completing the loop twice.

Alright, I've added that to the guide, with a note that it's not currently known what it means to "complete a loop 2 times". I assumed the reason was ambiguity and not sheer difficulty. So correct me if I'm wrong.

Double Dog's description appears to be "Complete a loop 2 times". I still haven't been able to do it personally, but looking at the community hub for the game, there's a few users who appear to have unlocked it.

Yeah, that's strange. I had to log out to see that. I guess I just started playing before really taking a closer look at the game's achievements.

I think you might be mistaken, or have already earned the achievements. When I look at the achievements page, there are three (3) secret achievements not shown. Going to the global page reveals their names, but not their descriptions: Traitor Dog, Warp Dog, Double Dog

The page accessible through Steam.

Huh. Could you be a little more specific? I'm not aware of what you're referring to by "the achievements page". Did somsone write a guide? Did the dev add an achievements page to the game menu? Or are you just talking about the achievement listing page on steam?

The only one in that list that's a secret/truly unknown is Double Dog. Traitor Dog and Warp Dog both have their requirements listed on the achievements page (assist an enemy in killing another enemy and unlock all warp zones) though I imagine when you made this guide originally those weren't on the page yet.

Double Dog's achievement graphic has 9-1 in it, so it must be tied to getting to that level. I've not been able to get that far personally, unfortunately, since once you hit those levels you'll be attempting to race against a blue saw blade to exit the levels and it's quite easy to make mistakes while trying to get to the bone.

Grabbed the image from google images cause steam forced me to include an image.