Perhaps this is just a projection of a square from a non-Euclidean space in which the lines are in fact straight and parallel.
I think the 2D surface of a cone (or double cone) would be an appropriate space, allowing you to construct this shape such that angles and distances around geodesics are conserved in both the space itself and the projected view.
This shape in that space would have four sides of equal length connected by four right angles AND the lines would be geodesics (straight lines) that are parallel.
I don’t remember all my geometric rules I guess, but can an arc, intersecting a line, ever truly be a right angle? At no possible length of segment along that arc can you draw a line that’s perpendicular to the first.
An infinitely small segment of the arc can be.
Geometrically there isn't a problem. If you draw a line from that point to the center of the arc, it will make it clearer.
I guess if we define it as a calculus problem, I can see the point..
I didn’t mean to pun but there it is and I’m leaving it. Any way, there is no infinitely small section that’s perpendicular. Only the tangent at a single (infinitely small) point along a smooth curve, as we approach from either direction. Maybe that’s still called perpendicular.
A right angle exists between the radius of the circle and the line tangent to the circle at the point that the radial line intersects it. So we can say the radius forms a right angle with the circle at that point because the slope of the curve is equal to that of the tangent line at that point.
I think that, in order to have this be a projection of a square, the space between the interior right angles of the space from which it was projected would have to be not just curved, but also twisted, like a Möbius strip, such that a person "walking" the square and starting from the rightmost angle leftward would start walking as if they were on your screen (their head coming out away from the screen), but then they would need to have their perspective twist so that they are now walking on the "underside" of the figure (their head now pointing into your phone). This would allow them to perceive the two "external" turns as "internal" turns, as well. Then it just needs to untwist on the way back. We just can't see the twisting, because the lines have no width.