Trend lines, running at a certain angle between the minimums and maximums on a graph, are called Gann lines in honour of the legendary 20th century trader who developed this trading system. A perfect Gann trend line is considered one which runs at a 45 degree angle, thus being the ideal correlation between time and price which are measured proportionally equal. When prices edge closer to this line, demand and supply are balanced, and with any break above this line, a bull trend is said to have come about. Conversely, any break below this line from above is considered as a bear trend. Since a trend line at a 45 degree angle is considered perfect (and thereby unattainable in reality), Gann marked out 8 other different angles which represent more flat and more slanted trend lines.