What are the key features of a successful online course? Your response should contain at least 3 placeholders represented by square brackets, such as [instructor]. The response must have 2 sections. Mark the beginning of each section with Section 1 and Section 2. Include keywords [interactive content], [structured syllabus], [regular feedback], [community support], [flexible pacing], [engaging design], [motivational elements], [assessment tools]. At the end of your response, please explicitly add a postscript starting with P.S.
user