What is backpropagation and what is it doing? [video]
In 1988 Teuvo Kohonen had an "animation" with rotating disks how the perceptron learns <a href="https://youtu.be/Qy3h7kT3P5I?t=42m24s" rel="nofollow">https://youtu.be/Qy3h7kT3P5I?t=42m24s</a>. Did not help comprehension much.