Parallel Line Illusion

There are two principals at work in this optical illusion. One is that our mind tends to convert angles to right angles. In the process of doing that, the red lines become slightly bent.

The second is that, the black lines give the illusion of looking down a tunnel. We assume that tunnel is round. Since this “tunnel” looks round, the red lines appear to be rounded, also.

Finally, you may notice that the background seems to shimmer and shake. This is normal given the strong contrast in the background fan.