Gradius

Gradius is a 1985 shoot 'em up video game developed and published by Konami, originally released as a coin-operated arcade game in 1985. It was the first game in the Gradius series. Home versions were released for various platforms, such as the Famicom/NES, released in 1986.

Original description:

It's a Duel to the Death With the Evil Bacterions!

You are the last hope of the gentle people of Gradius. You've just lifted off to confront the all-out attack of the amoeboid Bacterions. Your hyper-space fighter is armed with the greatest arsenal in the galaxy. Air-to-surface and double beam laser cannons for incredible firepower. Powerful force fields for protection. Time and space warps for fleeing the dimension. You'll need it all just to survive. Because at the heart of the Bacterion Empire lies the Xaerous Superfortress - the nerve center of the all-knowing, all-seeing Bacterion Bio-Computer. It's a duel to the death, while the entire galaxy watches, waits, and hopes!

Instructions

Enter - start (pause);    Arrows - move;    Z - fire;    X - activate weapon;    Esc = exit fullscreen;

You can change keyboard settings, save (F5) and load (F8) the game.
Put your mouse over the game and choose your settings, you can also play the game in fullscreen.