What makes the flag of the Philippines unique?

The National Flag of the Philippines is a horizontal flag with equal bands of royal blue and crimson red, with a white, equilateral triangle at the hoist (the edge of a flag nearest to the flagpole). In the centre of the triangle is a golden-yellow sun with eight primary rays, each representing a Philippine province. At each vertex (corner) of the triangle is a five-pointed, golden-yellow star, each of which represents one of the country's three main island groups. The white triangle at the flag represents liberty, equality, and fraternity.

The unique feature of the flag is its usage to indicate a state of war if it is displayed with the red side on top, which is effectively achieved by flipping the flag upside-down. To indicate a state of war, the red field is flown upwards and is placed on the right (i.e., the observer's left) when hung vertically. In times of peace the blue area is the superior field of colour.

The orientation of the flag was used during the Philippine–American War from 1899 to 1901, World War II by the Philippine Commonwealth from 1941 to 1945 and by the Japanese-sponsored Philippine Republic when it declared war against the United Kingdom and the United States in 1944, the attempted coups d'états during President Corazon Aquino's administration, and EDSA III (protests held for seven days in 2001 in a major highway in Metropolitan Manila, the Epifanio de los Santos Avenue (EDSA)).