not receive wide acceptance and was not a popular script even among the elite Mongols themselves, although it was used as an official script of the Yuan dynasty until the early 1350s when the Red Turban Rebellion started. After this it was mainly used as a phonetic gloss for Mongols learning Chinese characters. It was also used as one of the scripts on Tibetan currency in the twentieth century, as script for Tibetan seal inscriptions from the Middle Ages up to the 20th century and for inscriptions on the entrance doors of Tibetan monasteries. Syllable formation Although it is an alphabet, phagspa is written like a syllabary or abugida, with letters forming a single syllable glued or 'ligated' together. Unlike the ancestral Tibetan script, all Phags-pa letters are written in temporal order (that is, /CV/ is written in the order C–V for all vowels) and in-line (that is, the vowels are not diacritics). However, vowel letters retain distinct initial forms, and short /a/ is not written except initially, making Phags-pa transitional between an abugida, a syllabary, and a full alphabet. The letters of a Phags-pa syllable are linked together so that they form syllabic blocks. Typographic forms Phags-pa was written in a variety of graphic forms. The standard form (top, at right) was blocky, but a "Tibetan" form (bottom) was even more so, consisting almost entirely of straight orthogonal lines and right angles. A "seal script" form ( ; "Mongolian Seal Script"), used for imperial seals and the like, was more elaborate, with squared sinusoidal lines and spirals. This 'Phags-pa script is different from the 'Phags-pa script, or 八思巴字 in Chinese, that shares the same name but its earliest usage can be traced back to the late 16th century, the early reign of Wanli Emperor. According to Professor Junast 照那斯图 of the Chinese Academy of Social Sciences, the later 'Phags-pa script is actually a seal script of Tibetan. Korean records state that hangul was based on an "Old Seal Script" (古篆字), which may be Phags-pa and a reference to its Chinese name 蒙古篆字 měnggǔ zhuànzì (see origin of hangul). However, it is the simpler standard form of Phags-pa that is the closer graphic match to hangul. Letters Basic Letters The following 41 are the basic Phags-pa letters. Letters 1-30 and 35-38 are base consonants. The order of Letters 1-30 is the same as the traditional order of the thirty basic