This guide explains the technical aspects of creating a notification-based one-on-one call application called Blitz. The app is powered by 100ms and Firebase, enabling users to make video or audio calls with features like Call List UI, Self-Preview, Call Options, and Call Notifications. Key technologies used include WebRTC for real-time communication, Firebase Cloud Messaging (FCM) for push notifications, and Apple's CallKit for native call interface on iOS devices. The guide also provides step-by-step instructions to set up the Blitz app using 100ms Prebuilt UI components and customizing it with a tailored calling interface from the hms_room_kit package.