The Gupta script (sometimes referred to as Gupta Brahmi script or Late Brahmi script) was used for writing Sanskrit and is associated with the Gupta Empire of the Indian subcontinent, which was a period of material prosperity and great religious and scientific developments. The Gupta script was descended from Brāhmī and gave rise to the Śāradā and Siddhaṃ scripts. These scripts in turn gave rise to many of the most important Indic scripts, including Devanāgarī (the most common script used for writing Sanskrit since the 19th century), the Gurmukhī script for Punjabi, the Bengali-Assamese script, the Tibetan script and possibly also the distant origin of Hangul if based on Ledyard's theory. The Gupta script was descended from the Ashokan Brāhmī script, and is a crucial link between Brahmi and most other Brahmic scripts, a family of alphasyllabaries or abugidas. This means that while only consonantal phonemes have distinct symbols, vowels are marked by diacritics, with /a/ being the implied pronunciation when the diacritic is not present. In fact, the Gupta script works in exactly the same manner as its predecessor and successors, and only the shapes and forms of the graphemes and diacritics are different. Through the 4th century, letters began to take more cursive and symmetric forms, as a result of the desire to write more quickly and aesthetically. This also meant that the script became more differentiated throughout the Empire, with regional variations which have been broadly classified into three, four or five categories; however, a definitive classification is lacking, because even in a single inscription, there may be variation in how a particular symbol is written. In this sense, the term Gupta script should be taken to mean any form of writing derived from the Gupta period, even though there may be a lack of uniformity in the scripts. The surviving inscriptions of the Gupta script are mostly found on iron or stone pillars, and on gold coins from the Gupta Dynasty. One of the most important was the Prayagraj (Allahabad) Prasasti.