A system for generating videos uses a domain-specific instructional language and a video rendering engine that produces videos against a digital product which changes and evolves over time. The video rendering engine uses the instructions in an instruction markup document written in the domain-specific instructional language to generate a video while navigating a web-based document, (which is different from the instruction markup document), representing the digital product for which the video is generated. The video rendering engine navigates the web-based document, coupled with the instruction markup document, which explains the operations to be performed on the web-based document. The instruction markup document also identifies the special effects that manipulate the underlying product in real-time, includes the spoken text for generating subtitles, and provides formalized change management by design.