Well yes, the counting of footsteps was another game idea, this wouldn’t work here, because the footsteps sounds are not consistent with distance. A major challenge i found is, that evaluating distances with audio only is incredibly hard, just due to the nature of how sound is scaling, because it is not linear. The volume ramps up when something is really close and then fades slowly. So i don’t think a mental map based on specific unit works. But what i do think is, that you still need the ability to give relative information to a player. Like, there is a big rock to the right of the enemy etc. which is also a way to build a mental map, just relative.
And it is in fact possible to know how much you turn, or how much you strafe etc. If you’re in front of an obstacle the ping will be dead center. Once you walk sideways it will gradually move to the right or left side. That way you can gauge how far you have walked, relative to that obstacle. And now you can try to walk forward an see if you are already past the obstacle (because the size of the thing is another challenge to communicate) and will get an directional bump sound if you hit it. And that sound then tells you how much more you need to walk to the side. If the bump is still in front, it means you need to walk way more sideways, if its to the sides, it means you’re almost past it. Thats btw a good reason for the obstacles beeing circular, because this allows for this gradual directional response.
And the degree of turning btw works the same. You can center yourself towards an obstacle ping. And now you can turn gradually, untily the ping appears completely to one side. Now you know, that you turned 90 degrees, relative to that obstacle.
Btw, that idea with an additional kind of proximity sensor also crossed my mind, but dunno if that gets to crowded too fast. Plus, the enemy actually has a hum, that you can better locate him when close.