I'm a recovering completionist. Don't do this to me! I've been trying to find a secret area by walking on the pipes but that is probably a red herring. But why is there a gauge there? I also haven't found the girl on the roof yet, multi-wall jumping doesn't seem to work :)
SPOILERS AHEAD (for another game, which you should have played by now, if you enjoy this game, in my opinion) There's also a hiss at the industrial site which reminds me of the game Full Throttle where you have to kick the wall at the right time. But that can't be a thing, right? But the gauge!
In one of the alleys there a trash can with one open lid and a small box on the ground next to it/ You notice an exterior stair just above teh trash can. You hop on the box, then the closed side of the trash, then the open, then the stairs. I'll leave the rest of the puzzle for you to figure out. You want to make it to the top of the building.
Thanks! That was fun. I think I got on top of most things with some glitch exploiting save for the green water tower next to the secret person. I got to the UFO but it didn't trigger a secret sequence with the sunbathing space-person. I also got into the sewer pipe but I didn't find any more secrets there. Maybe we need to combine our powers and do the secret emoji sequence. Or maybe spin the sigils in the title sequence to enable cheat mode. :-)