Bastion

It's 1986. Again.

Sebastian Parker had lived a long life, one that most would consider successful as a writer of science fiction. Mastering his craft had been the work of decades, but when the world came under assault from actual aliens, the war demanded more from every person... and Sebastian was no exception. Too old to fight, he contributed the only ways he knew, and that drew him deeper into the last gasp of humanity's struggle for survival until, one day, his own struggle came to an end.

and then he woke up.

A century earlier, his body once more that of his youth, his memories split between the world's dark future and his own childhood. He would have considered it all a dream, except for one unassailable piece of evidence. Alien technology he had known had come back with him, and now he looks to the future and sees only the coming storm.

Sebastian and his Virtual Intelligence companion, Al, must now set a course from the 1980s to the future and the distant threat... only to find the threat isn't so distant, and the future isn't so certain. Armed with knowledge of the future, an occasionally snarky Virtual Intelligence, and absolute disgust at the sheer number of genre tropes he's dealing with, Sebastian begins making his plans the only way he knows how... guided by his familiarity with fiction and gaming and his knowledge of what is to come.

The countdown has begun, the threat is here, and he's the only one who can stand as a Bastion against the Dark Future.