Can you have "directional" wireless power transmission (to power an LED)
My idea was to use &quot;wireless power transmission&quot; (because I don't want to put a battery in the object) and then control the direction of the field to dictate which LED lights up (similar to a &quot;biderectional LED&quot;). But I can only find circuits that use AC (to be more efficient‽), either with a capacitor &amp; transistor or just a transistor and &quot;self oscillation&quot;.

Polarity will not work; this sort of &quot;wireless power transmission&quot; is really a transformer, and transformers only pass AC.
You could potentially use the orientation of the field, ie, have two solutions at right angles to each other, but a lot of contemporary solutions have the field oriented vertically, so that won't work either.
Instead, what you'd probably want to do is to modulate information in a detail of the drive signal - possibly something as simple as a small change in frequency, or a pattern of pulses and gaps.
Or you could just use some cheap radio technology.
The advantage of the latter is that you could give in and use a battery for power after all, which you're likely to find quite a bit easier to get working.
Easiest still would be a battery and some reed switches, and then put magnets or electromagnets in the base; then you don't even need to do low-power design to preserve your battery, since the reed switch functions as an actual switch.