My first idea, but probably too complex
I was just thinking of the old Ghostbusters game on C64.

The goal was to earn enough money to pay back your bank loan before the city's PK Energy reached 10,000. There were always four yellow ghosts traveling to the center "Zuul" building, and the energy jumped when they did, so you delayed the inevitable arrival of Gozor by catching them.
That's my thought process now, a game where you eventually have a big showdown, but you just have to delay it as much as possible so you'll be better prepared to deal with it.
My thoughts are the scope is too big, though.