What are the key features of a successful online course? Your response should contain at least 3 placeholders represented by square brackets, such as [course_title]. Highlight at least 2 sections in your answer with markdown, i.e. *highlighted section*. Include keywords [interactive elements], [course structure], [student engagement], [learning outcomes] in the response. In your response, the word [interactive] should appear at least 2 times. Your entire response should be in English, and in all lowercase letters. no capital letters are allowed.

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