ES - I just noticed something on the current intra-day chart that I had to post. From the beginning of the fall Thursday afternoon, I was looking for a full 360° fall down to 866. If we take another 360° move from that 866 level (thus, a 720° from the top), we have 829.25! This is dead on to where we stopped this big fall. Incredible!
To better illustrate this, I updated my Gann script to handle degrees larger than 360°. The chart below better illustrates the progression from Thursday's high, down to Friday's low (720° rotation (2x360)), then a return to the 180° mark by Friday's close. Again, what's amazing about this, are these levels are calculated using a single number, 903.50 (small blue dash on chart).
Gann theory: Many, if not most, major stock market moves end on a multiple of 90°.

Taking a measurement from the bottom up, starting at the very start of the upward move, we see that once the market opened, it completed the move to the 180° level and found resistance. We then retraced to the 90° (notice a bounce off the center level (90°+45° = 135°) on the way down).
While on the subject of a 720° move. This next chart is mind boggling to me. This is the weekly ES chart, taking a calculation from the Oct 2007 high (1586.75), you see we made a 720° rotation (to the TICK!) down to the recent November low (739). You can see we retraced back to the 540° level (360° + 180° = 540°).

Lesson