A two-dimensional being, living in a flat, two-dimensional world, would perceive a three-dimensional being in a rather limited way. Let's consider a hypothetical scenario where a three-dimensional object, such as a sphere, interacts with a two-dimensional plane inhabited by the two-dimensional being.
The two-dimensional being would only see cross-sections or slices of the three-dimensional object as it intersects their two-dimensional plane. For example, if a sphere were to pass through the plane, the two-dimensional being would initially perceive a small point, then a growing circle, followed by a shrinking circle, and finally a point disappearing as the sphere moves out of the plane.
The two-dimensional being would have no direct perception of the depth or volume of the three-dimensional being. From their perspective, the three-dimensional being would appear as a series of changing shapes and sizes as it intersects their two-dimensional plane.
However, it's important to note that this depiction assumes that the two-dimensional being has the ability to perceive and interpret the intersections accurately. Since our understanding of two-dimensional beings is hypothetical, it's challenging to precisely determine how they would perceive or interpret the interactions with a three-dimensional being. The concept of visual perception would likely differ significantly in a two-dimensional world compared to our three-dimensional experience.