Work together to make the Delorean reach 142 km/h and return to the future.

Not so fast! Because of all that time travel of Marty and Doc we have a number of time paradoxes. If the Delorean goes through such a paradox, there will be a chain reaction that will tear the space-time continuum to shreds and destroy the entire universe!
Work together to solve them or there may be no future at all!