Launch Alligator Flash Designer. Set movie dimensions, 400 x 400 pixels: "Frame" > "Frame size".
Creating a square Choose the "Rectangle" tool and draw a small rectangle. Choose "Item" > "Resize" and enter 32 x 32, click OK.
Duplicate the square Choose "Edit" > "Duplicate and duplicate the item 8 times horizontally. Set "Step Y" to "0", for "Step X" type the width of the square plus some margin for example try 40 pixels, type 7 as the count.
Select all squares and choose "Edit" > "Duplicate" again. Set Step X to 0 and Step Y to the same as before for example 40 pixels.
Delete few squares (about 1/4 of them) - click on a square and press "Del" key.
Creating the move Pres Ctrl+A to select all items. Choose "Frame" > "Animation Wizard". Uncheck "Synchronized" options.
Click OK.