We have the heat, the air, the water, thoughts and feelings. It is impermanent. When we contemplate the body we can experience that microscopic level of that constant change and flux. And we can experience this directly. There is no separation between yourself and the green mountains.
Green mountains come forth as self.
Turning the light around and looking back is the path of the ancient ones, the mountains and waters of the immediate present. However there is more to the Buddha's teaching than the realisation of emptiness. We must not stagnate in that realisation of emptiness. That must be replaced by a more comprehensive realisation of integration, and that integration is merging with the world in compassion. We do this dance in many ways continually, back and forth.