What are some alternatives?
When comparing Terrastruct and Page Flows, you can also consider the following products
SnapUp - Wireframe faster / create amazing user interfaces
UX Archive Animated - iOS apps animated user flows
Plectica - Easily diagram anything, together
User Onboarding - Onboarding teardowns of popular sites/services
Whimsical Wireframes - Lightning fast wireframing with real-time collaboration.
UI Movement - The best UI design inspiration, daily