- Defender (Atari 2600) online game (atarionline.org)
ATARI DEFENDER is very similar to the Williams coin-operated DEFENDER game. However, you will find some differences in the game play as well as in the graphic images and game controls. For example, in the coin-operated DEFENDER game, two or more Alien Landers can kidnap Humanoids simultaneously, whereas in the ATARI version, Landers can abduct only one Humanoid at a time. In the coin-operated game, you can accidentally kill a Humanoid with your own missile fire while attempting a rescue, and even lose a life in Hyperspace. Such tragedies cannot happen in ATARI DEFENDER. ATARI Humanoids are invulnerable to missile fire, and Universal Space Ship Defender will always emerge from Hyperspace intact.
- Potassium (Wikipedia)
Potassium is a chemical element; it has symbol K (from Neo-Latin kalium) and atomic number 19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to form flaky white potassium peroxide in only seconds of exposure. It was first isolated from potash, the ashes of plants, from which its name derives. In the periodic table, potassium is one of the alkali metals, all of which have a single valence electron in the outer electron shell, which is easily removed to create an ion with a positive charge (which combines with anions to form salts). In nature, potassium occurs only in ionic salts. Elemental potassium reacts vigorously with water, generating sufficient heat to ignite hydrogen emitted in the reaction, and burning with a lilac-colored flame. It is found dissolved in seawater (which is 0.04% potassium by weight), and occurs in many minerals such as orthoclase, a common constituent of granites and other igneous rocks.
- Defender (1981 video game) (Wikipedia)
Defender is a horizontally scrolling shooter developed by Williams Electronics in 1980 and released as an arcade video game in 1981. The game is set on either an unnamed planet or city (depending on platform) where the player must defeat waves of invading aliens while protecting astronauts. Development was led by Eugene Jarvis, a pinball programmer at Williams; Defender was Jarvis’s first video game project and drew inspiration from Space Invaders and Asteroids. Defender was demonstrated in late 1980 and was released in March 1981. It was distributed in Japan by Taito.