The core mechanics are energy exchange. Energy exchange can happen only on the distance proportional to the creature's energy capacity. So the creatures need to be close enough to be able to exchange energy.
All world transversal mechanics are based on point of interest. Creatures would automatically walk to the point of interest if they're close by, and fly if they're far.
<aside> ⚡ All mechanics involving energy are going through redesign. The main change is that changing own lightness is a free choice. Here is old version
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