(another riddle, not as long as the last)
The mysterious and shadowy contact who set you up with that formerly-haunted house was impressed enough with how you dealt with the infinite basement that they've got another job for you. There's this ballroom that's recently been de-ghosted, and you've been asked to join the team that's doing the initial post-deghosting inspection of it.
So you show up at the address you're given at the time you're given plus five minutes, but that's okay because apparently the Spooky Architecture Team are going to be ten minutes late. It's an extremely windy day outside and the door's unlocked so, spending very little time considering the safety of entering another formerly-haunted building, you let yourself in.
It really is a magnificent room; a huge (but finite and bounded) domed ceiling lets in a lot of natural light, and the floor is made of a whole spectrum of coloured tiles. The tile pattern is interesting: it's a perfect tesselation of regular seven-sided shapes (meth, eth, prop, but- oh, heptagons), all identical in size and shape, with three around each corner where the tile edges meet. It must have taken a lot of effort to tile the entire hall with this pattern, in such a wide array of colours (it's an old building! What are these pigments?), and get it to all lie perfectly flat and smooth so it's suitable for dancing.
You're pacing around the room waiting for the SAT to arrive (they're now fifteen minutes late). You walk forward ten meters, turn 90 degrees to the right, walk forward another ten meters, turn 90 degrees right and walk forward ten meters again - at which point you stop, noticing that, somehow, you're closer to the point where you first turned right than you are to the point where you started.
The question is: how is this possible?
Hints/the solution/commentary will (probably) be added later. For now, you're on your own! Hints are in another post because what the heck I can unnecessarily bump my own posts, see here.