Watched this film a second time today. Few months back, when I watched this, so many things were unclear. Now lot of things make some sense. CJ missed the science fair so that her invention could be put to a more personal use. Since he was protective of CJ,Calvin Walker knew that he could in potential conflicts with law authorities. Sebastian knew constant time jumps and touch with old selves could put them in trouble, which is what happened later. A brilliant film on individual actions causing ripples on time-space which we can't correct easily. I believe CJ could be dead in the final scene as she says "I love you Sebastian " and takes a risk. She is also haunted by guilt, and so I think she will give the machine to Calvin Walker. What distinguishes this from Back to the Future series is that the sense of spectacle is dimmed in SYY and the emotions feels very real. The science aspect is also given more weightage as compared to Back to the Future. However, there are a few things which prevent SYY from being perfect, the cops acting was terrible and they were in plainclothes taking away the seriousness of that scene. CJ was shown as dumb/rude in some scenes, which felt out of place with the tone of the film. Also at a physical level, the constant jumps don't change either VJ or Sebastian which is baffling.