Ok...let's try again...
If you focus on tiny details, particels, how attention movesfrom one detail to another, or if youjust stay with whatever ever-changin visual effects, then you are focusing on impermanence, and this will create insight into the 3C
On theother hand, if you focus in a way that the circle seems to be basically solid, always the same, then insight won't arise and concentration will get strong very quickly.
I'm pretty sure that there isno way you can possibly stare at an object and not seeing any impermanence-related visual effects after awhile, wich is to say, there is no obvious way to separate the two from a practical point of view.
However, your intention will make things different somehow.
If you want to get insight from it, you can play with various ways you can tune your attention; so,for example, you can see how every moment you percieve only one detail and the next moment you percieve another one, or how attention bouces from the visual field to your body and how when one id there theother isn't,or you can play with the fact that one moment attention is on the main object and the moemnt after has bounced to see the periphery, or just relaxing into any kindof ever-changing visual effect that eventually will arise, or how there seems to be some kind of tension around the eyes that you can let go of, or how in general trying to concentrate seems to create some kind of effort and tensing in your body, or just tuning into the fact that there is no reason for you to focus because, since you have eyes and you stated before the intention to see it, then seeing will happen regardless, or whatever else you can come up with to get insight in one of the 3C.
If you want to get your concentration strong, you can make an adjustment and repeat "red...red..." in your mind to slow down mental proliferation; also, adding some mantra-component will help with concentration in general.
If you want to get jhanas, you just wait until plaesent sensations arise, and then just enjoy them, sinking into them.
If your concentration gets strong but plaesent sensations don't arise, you can begin to repeat in your mind "joy...joy..." and this will probably do the trick, because when the mind is concentrated it's much more responsive and obedient.
Another trick to get first jhana with a visual object is to focus your eyes in a way that is like if when you focus on a narrow object;
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