Hit the green flag. If this works you will think the biggest lines are slanted, but they are vertical.
My other eye trick program was immediately given attention so I thought I would do this. Upon request, although this may be entirely wrong since it is my best guess from my experiences with illusions of this sort. I believe that the lines look slanted after I added the mini tilted lines because your brain tries to figure out which way the vertical lines are pointed and while it does that it takes into account the mini lines. While it does that it may be assuming that the mini lines are close to perpendicular to the vertical lines, and thus your brain may interpret the vertical lines as slanted to get them close to perpendicular. If you take note, the vertical lines seem slightly slanted by adding just one set of mini lines, but incredibly more so after you add the second set. So my second guess is that your brain sees a back and forth pattern with the mini lines and assumes the other lines are also back and forth. Again, I am not a scientist, so take all that with a block of salt.
