Space Invaders

Space Invaders is an arcade game published by Taito Co., Ltd. in 1978. Space Invaders is the biggest hit in the history of arcade games and the earliest example of a shooting game. Similar products and bootlegs have been made by other companies such as Irem's IPM Invader.

Space Invaders

Arcade flyer

Developer:	Taito
Program:	Tomohiro Nishikado
Release date:	Arcade: 1978

Gameplay Overview

Each level tasks the player with destroying a 11 x 5 grid of aliens. The wave moves left or right, shifting down a row and reversing direction at either side of the screen. The speed of the wave is divided by the number of aliens (since only one can be updated each frame). Consequently, as aliens are destroyed the rest become exponentially faster. The cannon can only move horizontally, and shoot straight up (if a bullet is not already in play). Each level has four destructible shields that block both player and enemy shots. The player starts with three cannons and can earn a fourth by obtaining 1500 points. If all cannons are lost OR the aliens reach the bottom of the screen, the game ends.

Controls

• 2-way Joystick: Horizontal movement
• Button (Press): Fire

Scoring

• Octopus : 10 points.
• Crab : 20 points.
• Squid : 30 points.
• UFO : ??? (50, 100, 150, or 300) points.

Characters

• 

  Octopus
  Large invader.

• 

  Crab
  Medium invader. The official mascot of Taito.

• 

  Squid
  Small invader.

• 

  UFO
  Mystery ship that appears occasionally.

• 

  Cannon
  Player's spacecraft.

• 

  Shield
  A defensive wall.

Strategy

Basic Tips

• Shoot often and don't miss. Each time an alien is hit the wave stops moving for a quarter-second. Each missed shot takes a full second to cross the screen and explode.
• Destroy the wave's outer columns to decrease its width. This is the only way to permanently slow the invasion.
• Destroy the wave's inner columns to create a moving safe zone that aliens cannot cross.
• Position the cannon's center just past the edge of a barrier to shoot while being protected on one side.

Intermediate Tips

• Aim for the sides of aliens rather than their centers. This decreases the chance of shots being canceled by enemy fire.
• The faster the aliens, the safer it is to intercept them and the riskier it is to chase them.
• Always assume alien shots will squeeze through damaged barriers. Always assume alien shots will pierce through cannon shots.
• If aliens cannot be shot, shoot small shield pieces that might get in the way later.
• For an unknown reason, the last alien moves 50% faster when moving right instead of left.

Advanced Tips

• If an alien us directly above a barrier, it can be hit indirectly with a bullet explosion.
• If an alien is directly above a barrier, its shots can spawn past the thinner center.
• Enemy shots are not truly random. Knowing how they behave in the first few seconds of a wave is useful.

UFOs

Although UFO score was intended to be random, it actually cycles through the following numbers with each player shot: (50,50,100,150,100,100,50,300,100,100,100, 50,150,100,100)

• By hitting UFOs with the 23rd shot and every 15th shot afterward, each will award 300 points.
• The shot count can be increased quickly by hitting barriers.
• If a UFO awards 50 or 100 points, that means the player over or undercounted by one.
• Without shot counting, UFOs award roughly 100 points on average.
• A UFO appears every 25.6 seconds. By destroying 4 or 5 outside columns (so 6 or 7 remain) the invasion will last as long as possible.
• Although difficult, it's always possible to shoot between columns to hit a UFO.

Nagoya Attack

Nagoya Attack strategy

The Nagoya Attack (also known as the "Wall of Death") takes advantage of a bug wherein aliens on the last row spawn their bullets behind the cannon. By creating a safe space and only attacking enemies on the final row, the player is effectively invincible. At the same time, leaving most aliens alive until the last second slows the game so more UFOs can be shot. However, failing to destroy the last row of aliens perfectly results in the game ending instantly. This strategy is named after the city in Japan where it was presumably discovered.

This video demonstrates two common variations of the Nagoya Attack: https://www.youtube.com/watch?v=Ty2z6KP5X0Y

Trivia

concept art

• If the last alien of a wave is an octopus it creates a trail while moving right. This visual bug, nicknamed "rainbow", became a scoring feature in Space Invaders Part II.
• Space Invaders was inspired by the 1976 arcade game Breakout. Both games become more difficult as the number of targets decreases while the pace of gameplay increases.
• June 16th is officially recognized as the "Space Invaders Day".

References

1. https://en.wikipedia.org/wiki/Space_Invaders
2. https://ja.wikipedia.org/wiki/スペースインベーダー
3. strategy guides
4. Developer Interview "Looking back when Space Invaders was born"

Further Reading

1. Tomohiro Nishikado – 2000 Developer Interview
2. Space Invaders – 30th Anniversary Developer Interview