John Edathattil (credited, sometimes, as Sab John) is the screenwriter of Guna (1991). In this video, he talks about writing a script based on the Sri Lankan civil war for Kamal Haasan, and then writing Guna when that project was dropped. He speaks about writing through a personal crisis, and the various aspects of the character of Guna (the religious nature, the 'thaali', his hatred for his face) and more
