I invite you to create several optical illusions with me.
By Loucheman:
illusion 1
illusion 2
illusion 3
illusion 4
illusion 5
illusion 6
illusion 7
illusion 8
illusion 9
illusion 10
illusion 11
By Cymplecy:
Stepping feet using glide
By 800flans:
Trippy
By angzarr_812new
illusion 7.5
By codingisfun2831t
Orbisson illusion
By random_guy
hidden green arrow
I’ll begin with this project: Illusion 1.
It seems crooked!
I might make an illusion project 
I’m looking forward to seeing it
In this project: illusion 2, the orange ball on the right looks smaller than the one on the left, but they are the same size!
This would be more interesting if you could glide the left half to over the right half so the user could see that they’re the same size, then glide them separate again. (Otherwise there’s little point in making it a Snap! project instead of just showing us the snapshot. ;~P)
Alternatively, draw the two orange dots, then wait a couple of seconds, then draw the cyan ones.
I can do this, good idea
When I saw this, I wondered how much the gradients in the colors affect the illusion, so I tried editing the costumes. The answer is that I still see the illusion without the gradients, but not as strongly:
Like what you said to @loucheman - why don’t you make a project where we can experiment and modify the two colours?
I updated the project !
Because I am a lazy man !
Cool! :~D
Just for you: a new version of illusion 1
Sorry - I got confused- I thought Brian had made it not you 
if you choose the same color for color1 and color2: the illusion still work (because of the gradient)!
In this project: illusion 3, purple segment length is the same as the green one
Why not
I think it’s a illusion right
