I've updated all the sign-in links, "Start Free Practice" buttons, "Get Started" buttons, and the "Try Interactive Demo" button to point to https://app.toughtongueai.com/. All buttons now use the asChild prop with anchor tags to properly link to the external app while maintaining their styling and functionality.

I've successfully added a comprehensive blog section to the Tough Tongue AI website. The blog page features the complete PM interview study plan content with proper formatting, navigation, and visual hierarchy that matches the main site's design. I also updated the main homepage navigation and footer to include working links to the new blog page, ensuring users can easily discover and access this valuable content.