The Universe of Elemag

In Elemag, you cannot trust your eyes. Your eyes show you want is there, but only your ears will show you what you will feel.
Elemag is an alien universe in which electricity and magnetism as we know them are altered to become fully dual, with complementary analetric and katalectric charges. All fundamental charged particles come in ana-kata pairs--analectrons and katralectrons, anaquarks and kataquarks--creating two parallel forms of matter which both interact with light and gravity, but which can exist in the same space at the same time, and pass through each other nearly as if the other were not there. Magnetic effects give katalectrons and katatoms a small analectric dipole moment, and vice-versa, which can mediate inter-type bonds to produce mixed ana-kata materials that interact with both basic phases of matter, but this is the exception rather than the rule. Macroscopic permanent magnets, however, are unknown in Elemag--just as permanent electrets are difficult to create and find little use in our world, free complementary charges will move to cancel out any large-scale magnetic effects.
Because both anamatter and katamatter interact with light, but do not exclude each other from sharing the same space, simply seeing a wall in front of you or a piece of ground beneath you does not guarantee that you will run into it, or fail to fall through it! Sound waves, however, are largely confined to one phase--sound waves in katamatter interact only weakly with anamatter, and vice versa. The native inhabitants of this universe therefore rely heavily on sonar / echolocation to perceive and navigate their environment, always at least in tandem with and frequently in complete replacement of "normal" vision. The deaf--those who have lost their "first sight"--must walk with a cane for safety, like the blind of our world, but the blind (those without their "second sight"), in contrast, will face only minor inconvenience. The primary uses of vision in Elemag are for long-range perception (as, in appropriate environments, light travels farther and more coherently than sound, just as in our world) and high-detail perception (as the shorter wavelengths of light allow for much higher resolution than sonar clicks).