Time travel novels usually explore various different ways of transmigration, such as: 1. Time travel: Return to the past and change the course of history through time travel. 2. Space travel: Through portals, black holes, and other technological means to travel to other planets or cosmic space. 3. Soul Traversal: Transferring the soul into another body through a mysterious ritual or technical means. 4. Accidental travel: For various reasons, the body or soul travels to another time and space without prior planning or preparation. The main point of writing a time-travel novel was to let the readers imagine the scene of this time travel and be able to follow the actions and adventures of the protagonist. At the same time, they had to consider the various obstacles and challenges that might be encountered in the process of time travel and how the protagonist would overcome these obstacles to achieve his goal.