This is a prime example of the kind of shoot-'em-up that gives all of this sort of game a bad name by its mere association. The idea behind Defcom is based on the 'Star Wars' (SDI) defence system being designed at the moment. Apparently in 2056 the aliens tae over the fully implemented and deadly orbital defence systems and turn them towards Earth.
The game itself puts you orbiting above earth with your 'bog standard Eagle class E751'. Alien craft come at you from all directions with a selection of fast rotating globe below you that, I assume, is the Earth. Your weapons are a number of beam guns. Which ones you can use out of a possible four is decided by what your current score is. This can be checked, along with a map of the world, and which options have been set, by pop-up screens that ingeniously obscure the non-pausing on-screen action to your extreme detriment.
The game has largish moving objects that are quite quick, and some come at you from 'in' the screen, but use the kind of pseudo-3D effect that went out of the window years ago with Buck Rogers. The game is also very difficult to understand in some ways. The instructions go on about a deeper strategy to the game where you are defending different cities. However, the indistinct instructions and certain control difficulties make this aspect of the game a bit of a farce. Shoot-'em-ups should be quick and easy to understand, almost without looking at the instructions.
In a world of good, mediocre, and bad shoot-'em-ups, we don't need another bad one.