Since I saw many people saying the time travel in this didn't make sense or there was so many things unexplained, I tried to make a small explanation of it. Hope it will help if you are also confused. . . . The parallel worlds in normal state Let's assume A to H is there IP address and 1 to 8 are the mc in different age in red and blue parallel world. It's only possible to move between the same address. Meaning with the other self with their own age. 1 can only shift with 1 and 8 can shift with 8. But to time shift, 8 need to shift with 1. To do that, they need to change the spectrum of the bubble of the two worlds and push blue to the down. . . . The parallel worlds during the time shift Doing this will allow 8 from red to shift with 1 from blue. But in this case, instead of shifting, he just leave 8 to merge with 1 leaving the body in 8 brain-dead. . . . The visual representation shown in the movie This is the image from movie where they visualise this. They used the technology to cause a rift between the parallel worlds, causing the blue world to go down or in other word, to change address for a bit and parallel shifting in that exact moment allowed him to time shift. Now don't ask me how is this possible or what did they do, because it's fiction and they didn't go there for the obvious reason that it's fiction.