Optical Illusion - Mysterious Black Dots

This optical illusion is a variation on the previous optical illusion with the gray ghosts appearing in the intersections of the black grid.

We still have a black grid here, but now the lines are gray and there are white circles in the intersections. Have a look and try to count all of the black dots you see.

The black dots you see don't really exist. Whenever you try and look at one directly, it will disappear. I don't know why this happens as I haven't found a good explanation for it. Feel free to let me know if you have any insight into the comments.

The goal of this Instructable is to show you how to quickly recreate such a grid with a graphics program. You can then make some variations of your own.

To start with we'll want a gray background. Lock this or put it on another layer and then start making your building block.

We want to have a clean grid so that we're not distracted from the illusion by an uneven pattern.

To start, make a black square and make two identical smaller squares of another color. Attach these squares to the right and bottom of the black square.

These smaller squares will determine how wide the lines between the black squares are and are a guide for all the copying we'll be doing.

Now group the squares and let's go.

Copy the group and paste it directly to the right of the original group so that the small square just touches both black squares.

Now select all of the squares, copy them, and paste them directly below the first group. Use the little squares as a guide again to keep the distance consistent.

The results should look like the image below.

Create a white circle that fits right inside the intersection of the four black squares. This will take a bit of fidgeting to get the size and placement right, but make sure it fits well.

Delete everything but the original three squares and the white circle. You have now finished making the basic building block of this grid.

Use the small squares again as a guide as you copy and paste to create a row and then a series of rows to fill out the grid.

Delete the small squares and the circles on the outside to get your finished grid! You can now start chasing black circles of your own.

Now that you have the grid set up, it's a short step to making color variations to mess with your eyes even more. Check out the images below for different colors, combinations, and an inversion of the original.