I have to disagree with the Amazon review:
"After that, it's not hard to predict what's going to happen: government agents swoop in, but the story ends up in the "hands" of machines talking to one another. Thus we're stuck with flashing lights, etc."
You have to remember this film was brought out during the cold war and the era of the ZX Spectrum. Square blobs on a screen were impressive enough, but the idea of playing out multi-screen global nuclear war was enough to blow any 13 year old's mind at the time. This was combined with the fact that the computer software in question was named after the programmer's dead son and played the same kind of games, tic-tac-toe, that a child would. So, the final scene is not just about flashing lights, it's about a father teaching his son about life and the futility of war - and in so doing teaching every adult present in the US Army bunker the same lesson. This amounts to a very tense and touching finale.