Space Invaders
Space Invaders is a fixed shooter arcade video game designed and programmed by Tomohiro Nishikado and published by Taito Corporation in Japan on June 16, 1978.[1] In the game, a single player controls a laser-firing cannon that moves horizontally along the bottom of the screen to eliminate rows of descending aliens arranged in a formation, while dodging enemy bullets and using movable barriers for cover; the aliens advance inexorably downward, accelerating as their numbers decrease, with the game ending if any reach the player's level or deplete the cannon's lives.[2] The title introduced core mechanics of the shoot 'em up genre, including scoring bonuses for rapid successive hits, occasional high-value "mystery ships," and escalating difficulty through faster enemy movement and denser firing patterns.[3] Widely regarded as a foundational work in video gaming, Space Invaders propelled the arcade industry into its golden age by proving the mass-market appeal of interactive electronic entertainment, with Taito reportedly manufacturing over 360,000 cabinets worldwide and generating billions in revenue through widespread adoption in Japan and subsequent international licensing.[4] Its success stemmed from Nishikado's year-long development effort, which integrated hardware innovations like color graphics and sound effects with gameplay inspired by electromechanical games and war simulations, ultimately influencing countless titles and establishing shooter mechanics as enduring staples.[5] Despite persistent myths of economic disruptions such as a national coin shortage in Japan—debunked as exaggerated by arcade revenue hoarding rather than systemic scarcity—the game's cultural penetration led to dedicated "Invader Houses" arcades and inspired home console ports that further democratized gaming.[6]Gameplay
Core Mechanics
In Space Invaders, the player controls a single laser cannon stationed at the bottom of the screen, which can move horizontally along a fixed path and fire a single projectile upward at a time to destroy approaching aliens.[3] The cannon's movement is continuous but limited to the screen's lower edge, with firing triggered by a separate button, enforcing strategic timing to avoid overlapping shots.[2] The antagonists consist of 55 aliens arranged in five horizontal rows of 11, divided into three types by size and point value: larger cephalopod-like aliens at the bottom (10 points), squid-like in the middle (20 points), and smaller crab-like at the top (30 points).[2] These aliens advance as a cohesive formation, oscillating left to right across the screen; upon reaching either edge, the entire group descends one row and reverses direction, gradually closing in on the player's position.[3] The formation's horizontal speed remains constant per wave but accelerates progressively as aliens are eliminated, creating escalating pressure through reduced numbers.[3] Aliens fire downward projectiles at irregular intervals, targeting the player's cannon with shots originating from random positions within the formation to simulate unpredictability.[3] Four modular barriers, positioned midway up the screen, offer partial shielding; these erode progressively from player and alien projectiles, eventually crumbling to expose the cannon fully.[3] Periodically, a swift mystery ship traverses the top of the screen, evading standard patterns and awarding variable bonus points (50 to 300) if struck.[3] Game over occurs upon the destruction of the laser cannon by alien fire or if any alien reaches the bottom row, invading the player's defensive line; successful clearance of a wave advances to the next with renewed formation and barriers.[3] No reserve lives exist in the original arcade version, rendering each playthrough a single-attempt defense against endless waves.[7]Objectives and Progression
The primary objective of Space Invaders is to maneuver a laser turret horizontally across the bottom of the screen, firing upward to eliminate waves of descending aliens while evading their projectiles and preventing any aliens from reaching the ground level, which would result in the loss of a life.[2][8] Players start with three lives, depleted either by direct hits from alien fire or by alien invasion of the base line.[8] Progression occurs through sequential waves, each consisting of an 11-by-5 grid of 55 aliens arranged in five rows of varying types, which march left and right across the screen, dropping one row lower and reversing direction upon reaching screen edges.[3] Clearing all aliens in a wave advances the player to the next, with subsequent waves featuring faster baseline movement speeds and increased firing rates from the aliens.[7] Within each wave, the aliens accelerate as they are destroyed, a consequence of the game's Intel 8080 microprocessor design: fewer sprites reduce drawing time per frame, allowing the movement routine to execute more frequently and thus heightening pace toward wave completion.[9] Scoring incentivizes efficient play, awarding 10 points for large aliens in the bottom two rows, 20 points for medium aliens in the middle two rows, and 30 points for small squid-like aliens in the top row, with bonuses for rapid kills such as destroying eight aliens without missing shots.[2] Intermittent mystery ships traverse the top screen, yielding variable bonus points—typically 50, 100, or 300—depending on precise shot timing.[3] The game lacks a finite end condition, persisting until lives are exhausted, with high scores tracked to measure player endurance and skill.[8]Development
Conception and Influences
Tomohiro Nishikado, a Taito Corporation engineer, began conceiving Space Invaders in 1977, motivated by the success of early arcade titles and a desire to create a game featuring defensive shooting against advancing targets.[10] Initially, he explored military themes with tanks or airplanes as enemies, but abandoned these due to Japanese post-war sensitivities prohibiting depictions of human-on-human violence in games.[10] Nishikado shifted to extraterrestrial invaders, selecting aliens to avoid controversy while maintaining the tension of an existential threat.[10] Thematically, the game's premise of humanity repelling descending alien hordes drew from H.G. Wells' 1898 novel The War of the Worlds, which portrays Martian invaders launching cylinders at Earth and advancing relentlessly despite human resistance.[11] Nishikado modeled the invader sprites after marine creatures—squids for the squid-like aliens, octopuses for others, and crabs for the crab forms—to impart a monstrous, unfamiliar appearance suitable for otherworldly foes.[12] He explicitly rejected claims of Star Wars influence, as the film's Japanese release occurred after core development, and the game's pixelated aesthetic predated cinematic space operas in his design process.[13] Mechanically, Space Invaders synthesized elements from prior games, including Atari's Breakout (1976), which involved a defender breaking descending blocks, and Taito's Gun Fight (1975), an early vector-based shooter emphasizing precision targeting.[14] Nishikado aimed to evolve these by introducing enemy formation movement, barriers for cover, and escalating speed as invaders dwindled, creating psychological urgency from hardware-induced slowdown discovered during prototyping.[5] This fixed-shooter format prioritized simplicity amid 1970s hardware constraints, forgoing complex pursuits in favor of inevitable confrontation.[13]