Greetings, I would like to know if there is a simple way to create a Variable 3D Proximity/Distance Sensor. When you think about "Proximity Sensor" you think about "Infrared", but IR proximity sensors only ''scan" a straight line and not a whole spheric space, so that is not the answer. Detail 1: 3-dimensionality Imagine this: We have object A and object B. Object A has the sensor. Object A would sense object B's distance to itself (A) regardless of the relative position between the two objects - it wouldn't matter if B was in front of A, if it was on top of A, if it was behind A, etc. Detail 2: Variability The sensor would sense a variable proximity/distance. It would know if the two objects were 1cm apart, π cm apart, 12cm apart, 50cm apart, etc. Detail 3: Feelings :3 (Oh, Teh Loev) Imagine again objects A and B. Object A would only sense Object B's distance to itself. Not it's distance to a table, nor a wall nor your cat. Like if only Object A and Object B existed. Here's the catch: both objects would have the sensor and they would sense eachother (again, not anything else), so I can't use 'things' that would interfere with eachother (like, I don't know, isn't there something like the adding of sound waves[read phrase bellow]? I'm only a high-school student...). I thought about using sound waves (because they spread 3-dimensionally), but I don't know how I could implement that... Outcome This is an example of what the sensors could be used to after having the sensors built and the code written: 1: Object A senses B. Object B senses A. 2: If B is 50cm apart from self (A), light LED1. If A is 50cm apart from self (B), light LED1. 3: If B is 20cm apart from self (A), light LED2. If A is 20cm apart from self (B), light LED2. 4: If B is 5cm apart from selft (A), light LED3. If A is 5cm apart from self (B), light LED3. As you can see, in this example both objects would do exactly the same... Sooo.... How can I make such a PAIR of sensors that wouldn't interfere with eachother? P.S.: I'm talking about making a circuit of my own or buying a sensor and implementing it in an external circuit of my own or whatever... Thanks a lot.