Metroid

Metroid is the first game in the Metroid series. It was released first for the Famicom in 1986, and later for the NES in 1987. Set on the planet Zebes, the story follows Samus Aran as she attempts to retrieve the parasitic Metroid organisms that were stolen by Space Pirates, who plan to replicate the Metroids by exposing them to beta rays and then use them as biological weapons to destroy Samus and all who oppose them. Metroid was lauded for being one of the first video games to feature a female protagonist

Original description:

It's you against the evil Mother Brain in the thrilling battle of Metroid!

You're inside the fortress planet Zebes. The planet of endless secret passageways where the Metroid are multiplying. Left alone the Metroid are harmless. But in the wrong hands they could destroy the galaxy. It's up to you to prevent the Mother Brain that controls Zebes from using the Metroid for evil purposes. But that won't be easy. You'll have to use your spacesuit to absorb valuable energy for your search to gain the use of power items like the Ice Beam, Wave Beam, High Jump Boots and Varia. If you survive, it will be you and your acquired powers against the Mother Brain.

Instructions

When the game start, first go left and collect morph ball.

Enter - start (pause);   Arrows - move;   UP - aim up;   DOWN - turn into morph ball;
Space - switch between using your Beam Gun and Missiles;
Z - jump;    X - attack;    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.