Provide a response to the following question: What are the key features of a modern smartphone? Your response should contain at least 4 placeholders represented by square brackets, such as [model]. The response must have 3 paragraphs. Paragraphs are separated with the markdown divider: ***. Highlight at least 2 sections in your answer with markdown, i.e. *highlighted section*. In your response, the word "smartphone" should appear at least 2 times.
user