Defender

While it lacks the pop culture legacy of Pac-Man, Donkey Kong and Space Invaders, Defender, the first game created by Eugene Jarvis, is one of the most popular and most relevant video games of the arcade era.

The game's premise is simple: Defend a planet, and its 10 humanoid inhabitants, from abduction by hostile alien spaceships. The difficulty is in the implementation: Defender presents the player with a dizzying array of controls. The player's ship is controlled with an up-down stick, a thrust button, a fire button, a reverse button to change direction, a smart bomb button that kills all enemies on screen, and an Asteroids-style hyperspace button. And you have to keep your eye on an scanner that tracks out-of-range enemies.

When the game debuted at the AMOA (Amusement Machine Operators of America) trade show in 1980 -- which it almost didn't, due to the ROMs being loaded the wrong way -- visitors were afraid to go near its complex control panel. Observers decreed that Defender would fail in the arcades. These same observers thought Pac-Man was also doomed to failure, for being too repetitive. (The critics' darling? Rally-X.)

But Defender's revolutionary side scrolling, cutting-edge 16-color graphics, bold cabinet, fast action, and strong sci-fi storyline compelled arcade patrons to try their hand at its intimidating control panel. It took a while, but gamers eventually warmed to the difficult controls, and achieved scores the game's creators didn't think were humanly possible.

Why is Defender historically relevant? Its success proved that even casual gamers could handle complexity. Without Defender, it would have been risky for a company to release an arcade game that challenged the player to manage a joystick and six buttons... which didn't happen again until the first Street Fighter game, seven years later.

This game provides examples of:
 * AI Breaker: The Mutant Reverse Line.
 * Alien Invasion
 * Color-Coded for Your Convenience: The scanner.
 * Difficulty Spike: After only the first level, the game takes a disproportionate leap in difficulty. Somewhat justified, since it was an arcade game, and it needed to be over at some point so other people could play.
 * The Determinator: Mutants and Swarmers.
 * Earthshattering Kaboom: If all 10 of your humanoids die, your planet explodes, and the game becomes much more difficult. (If you survive a few levels, it's eventually restored.)
 * Enemy-Detecting Radar
 * The Golden Age of Video Games: This game was one of its biggest stars, especially among the hard core.
 * Hey, It's That Sound: Defender was Williams Electronics' first video game; they had previously produced only pinball machines. The sound effects in Defender all came from one of the company's earlier pinball games.
 * I Know Mortal Kombat: Joystik magazine reported, apparently seriously, that the U.S. Air Force was using Defender machines to help train its pilots.
 * Nintendo Hard: Not only is Defender insanely difficult for a first-time player, but after its success, design team Vid Kidz (Eugene Jarvis and Larry De Mar) adopted the attitude that a game should "kick the player's ass" -- their words -- the first time he tries to play it. They applied this philosophy to Robotron: 2084, a classic in its own right.
 * Stargate was even harder (another half-dozen new enemies, the namesake in-game gate, AND you get ANOTHER button (inviso) to try to keep track of. The game's chapter subtitle in one of the early guide books was "More difficult than flying a 747".
 * Planet Looters: With humans as the resource. If a Lander successfully abducts one, it becomes a dangerous Mutant ship.
 * Incidentally, the humans were an afterthought - earlier versions of the game lacked them, but Jarvis felt something was missing. Then he realized that the title was meaningless, because there was nothing to defend...
 * Sensor Suspense: Oh so very much.
 * Smart Bomb: Arguably the Trope Namer. Definitely the Ur Example.
 * Stalked by the Bell: The game spawns fast and short (thus hard-to-hit) Baiters to hunt down lollygagging players.
 * Wrap Around: The playing area is larger than the screen, but if you fly in one direction you'll end up back where you started (as if flying around a planet).
 * The Wrap Around was exploitable by skilled players, because your ship could cross this invisible boundary, but the aliens could not, so if you crossed the Wrap Around point, the aliens would all turn around and head the other way.