I have been reading the http://www.dharmaoverground.org/web/guest/dharma-wiki/-/wiki/Main/MCTB+The+Three+Doors
When the impermanence aspect predominates and is combined with the emptiness aspect, then the whole universe strobes three times quickly with something staring back at us as a minor aspect of that universe, and then it seems that awareness collapses into the space after the third gap, perhaps turning slightly towards the thing that was staring back. When the impermanence aspect predominates and is combined with the suffering aspect, then the three strobing moments feel wrenching, and the plunge into the gap feels fundamentally violating, like exactly the wrong thing to do. When the emptiness aspect predominates and is combined with the impermanence door, there are three clear and discrete moments of moving towards or sideways to (or perhaps focusing on) an intelligent seeing image staring back at us, except that there is nothing on this side. After the third moment, the illusion collapses in a very natural and pleasant way. When the emptiness door predominates with suffering as its second aspect, then a very strange thing happens. There is an image on one side staring back, and then the universe becomes a toroid (doughnut), and the image and this side of the toroid change places as the toroid universe spins. The spinning includes the whole background of space in all directions. Fruition occurs when the two have changed places and the whole thing vanishes. When the suffering aspect predominates and is combined with the emptiness aspect, again, the toroid thing happens, except that it can be quite distorted or cone-like. The universe can rotate up or down and away from us, so that the primary experience is of an image falling from this side, though with the hint that it might be coming back around to this side. When the suffering door aspect predominates with impermanence present, then the three moments in which the universe is ripped away from us are distinct. When the suffering door predominates, the experience is always a bit creepy.