11 min read

Threshold

Last updated: January 22, 2026

Overview

Threshold is a space-themed fixed shooter developed by On-Line Systems (later Sierra On-Line) and released in 1981 for the Apple II, making it one of the earliest titles from the company that would become synonymous with adventure gaming1. The game was inspired by Sega’s arcade hit Astro Blaster, though designer Warren Schwader chose to take the concept in his own direction rather than create a straight clone2. As Schwader stated during development, “Instead of trying to duplicate the game in every detail, I set out to just take the concept and run with it”2.

The game places players in command of the spaceship Threshold during a dark age for the Earth Federation, when humanity’s home planet is under attack and colonies are being raided unmercifully3. Players must defend against waves of increasingly aggressive alien enemies while managing limited resources including fuel and weapon heat levels4. Threshold achieved notable commercial success for its era, selling approximately 25,000 copies and receiving a Certificate of Merit for Best Science Fiction/Fantasy Videogame in 19832.

Story Summary

The narrative of Threshold is set during a desperate period in humanity’s future. “It is a dark age for the Earth Federation. Our home planet is under attack and our colonies are raided unmercifully. Space travel has become a death wish as more and more enemy ships find their way past the outer defenses and into the paths of friendly trade”3. This dystopian backdrop provides context for the player’s mission as an exploring space attack ship commander.

Players take on the role of a lone pilot defending humanity against waves of invading alien forces. With five fighters at their disposal, pilots must destroy multiple waves of enemy ships while using their hyperdrive capabilities to gain tactical advantages3. The mission involves progressing through the galaxy to encounter up to ten different enemy forces, each presenting unique challenges and attack patterns5.

The game’s tension comes not just from the alien threat but from the hostile environment of deep space itself. Pilots must remain alert for narrow tunnels they must navigate their ships through while engaging hostile forces5. The mothership can only resupply fighters after defeating enough enemies, creating a desperate survival dynamic that reinforces the game’s dire narrative setting.

Gameplay

Interface and Controls

Threshold employs a classic fixed shooter format where players control a spaceship positioned at the bottom of the screen4. The player’s vessel can move horizontally across the play field while firing upward at enemy formations. Control options include keyboard input on computer versions, with paddle support available on the Apple II version and joystick control on console ports1.

The game features two critical resource management systems that set it apart from simpler shooters of the era. The laser weapon has a temperature gauge that increases with each shot fired, and once it reaches maximum heat, the weapon becomes temporarily disabled4. Additionally, players must manage a fuel gauge that constantly depletes during gameplay4.

Structure and Progression

Gameplay progresses through waves of enemy formations, with each wave presenting increasingly challenging configurations of alien ships. After clearing a set number of waves, players receive a fuel refill from their mothership, creating natural gameplay segments4. The difficulty escalates as players advance, with later waves featuring more erratic enemy behavior.

  • Early Waves: Basic enemy formations with predictable movement patterns
  • Middle Waves: Increased enemy aggression and faster attack speeds
  • Late Waves: Enemies begin dive-bombing the player, requiring quick reflexes1

Players can activate a “warp drive” once per ship to slow down the action, providing a tactical option for overwhelming situations6. This limited-use ability adds a strategic layer to the otherwise fast-paced action.

Puzzles and Mechanics

While not a puzzle game in the traditional sense, Threshold requires careful management of multiple competing resources. The core mechanical challenge involves balancing offensive output against weapon heat buildup4. Firing too rapidly causes the laser to overheat, leaving the player defenseless, while firing too conservatively allows enemies to overwhelm defenses.

The fuel management system creates additional pressure, as players cannot simply play defensively while waiting for their weapon to cool4. Running out of fuel results in losing a ship regardless of combat performance, forcing aggressive play. The Atari 2600 version notably allowed vertical ship movement, which was unusual for fixed shooters of that era2.

Reception

Contemporary Reviews

Threshold received generally positive reviews upon release, with critics praising its challenging gameplay and resource management mechanics. The Book of Atari Software 1983 awarded the game a “B” rating2. JoyStik magazine gave Threshold 4 out of 5 stars in their 1983 review2.

The game was recognized by the industry, receiving a Certificate of Merit in the category of Best Science Fiction/Fantasy Videogame at the 1983 awards2. This recognition placed Threshold among the notable titles of the early 1980s golden age of arcade-style games.

Modern Assessment

Modern retrospectives have viewed Threshold as a competent but derivative example of the fixed shooter genre. MobyGames rates the game at 49% based on aggregated scores1. User reviews on My Abandonware rate the game at 5 out of 5 stars, though this is based on only 2 votes7.

Contemporary collectors note the game’s historical significance as an early On-Line Systems title. The ColecoVision version is considered moderately collectible, with a rarity rating of 6 for loose cartridges and 7 for complete-in-box copies8. Some modern commentators have acknowledged its relationship to Sega’s Astro Blaster, with one user noting “Great.. another Astro Blaster clone.. ready to try it..“7.

Aggregate Scores:

  • MobyGames: 49/1001
  • My Abandonware: 5/5 (2 ratings)7

Development

Origins

Threshold began as Warren Schwader’s attempt to bring the Astro Blaster arcade experience to home computers. Rather than creating a direct port, Schwader took a creative approach to the adaptation. “Instead of trying to duplicate the game in every detail, I set out to just take the concept and run with it”2. This philosophy resulted in a game that shared thematic elements with its inspiration while establishing its own mechanical identity.

Ken Williams, co-founder of On-Line Systems, contributed to the development, particularly working on the Apple II animation routines2. Williams spent approximately two weeks developing the animation system that would bring Threshold’s space combat to life on the Apple II hardware2.

Production

Development of Threshold took approximately two months to complete2. The game was programmed in machine language to achieve the performance necessary for smooth action gameplay on the limited hardware of early 1980s computers3. This was typical for On-Line Systems’ approach to game development during this era, as the company worked to establish itself in the competitive game market.

On-Line Systems, which would rename itself Sierra On-Line in 1982, was still operating from founders Ken and Roberta Williams’ home during this period9. The company had started modestly in 1979, and Threshold represented part of their early catalog as they built their reputation beyond their initial adventure game Mystery House9.

Development Credits:3

  • Designer: Warren Schwader
  • Programming: Warren Schwader
  • Animation Routines: Ken Williams
  • Publisher: On-Line Systems

Technical Achievements

Threshold demonstrated competent technical execution for its era, achieving smooth sprite-based gameplay on multiple platforms. The Apple II version utilized custom animation routines developed by Ken Williams over a two-week period2. The game’s weapon heat and fuel management systems added depth uncommon in fixed shooters of the period.

The multi-platform release strategy showed On-Line Systems’ ambition to reach the broadest possible audience. The game was eventually ported to eight different platforms, from the original Apple II to the Atari 2600, ColecoVision, Commodore 64, VIC-20, Atari 8-bit computers, and French Thomson computers1.

Technical Specifications

Apple II Version:1

  • Media: 5.25” Floppy Disk
  • Input: Keyboard, Paddles
  • Players: 1

Atari 2600 Version:1

  • Media: Cartridge
  • Size: 4 KB6
  • Publisher: Tigervision

ColecoVision Version:8

  • Media: Cartridge
  • ROM Size: 16 KB
  • Publisher: Sierra On-Line

Commodore 64 Version:7

  • Media: Disk/Cassette
  • Size: 8 KB

Version History

VersionDatePlatformNotes
1.01981Apple IIInitial release by On-Line Systems1
1.01981Atari 8-bitSimultaneous release1
1.01981VIC-20Initial console port2
1.01982Atari 2600Published by Tigervision5
1.01983Commodore 64November 1983 release10
1.01983VIC-20Additional release1
1.01984ColecoVisionMay 1984, Sierra On-Line branded10
1.01984Thomson MO/TOPublished by France Image Logiciel1

Technical Issues

No significant technical issues have been widely documented for Threshold, though the limitations of early 1980s hardware meant that each platform version had its own characteristics. The fuel depletion mechanic could prove frustrating for players who were unable to clear waves quickly enough, as this effectively created a time limit on each attempt4.

Easter Eggs and Trivia

  • Threshold was one of the games released under Sierra’s “SierraVision” brand during later releases3
  • The Atari 2600 version was unique in allowing vertical ship movement, which was unusual for fixed shooters of that era2
  • The game’s fuel management system was somewhat unusual for fixed shooters, adding a resource management element to the action gameplay4
  • Tigervision served as the publisher for the Atari 2600 version rather than On-Line Systems directly5

Legacy

Sales and Commercial Impact

Threshold achieved solid commercial performance for its time, with approximately 25,000 copies sold across all platforms2. This represented a notable success for On-Line Systems during the early 1980s, when the company was still establishing itself in the marketplace. The game’s Certificate of Merit for Best Science Fiction/Fantasy Videogame in 1983 provided valuable industry recognition2.

The multi-platform release strategy allowed Threshold to reach audiences across the fragmented home computer and console market of the early 1980s. The game’s appearance on eight different platforms demonstrated On-Line Systems’ commitment to broad market penetration, a strategy that would serve the company well as it evolved into Sierra On-Line.

Collections

Threshold has not been included in any official Sierra compilation releases. The game exists primarily through preservation efforts and retro gaming communities. Copies are available through abandonware sites and ROM archives, with the Internet Archive hosting playable versions for multiple platforms411.

Fan Projects

No significant fan remakes or modifications of Threshold have been documented. The game remains primarily of historical interest as an early example of On-Line Systems’ output before the company became primarily known for adventure games.

  • Original Game Manual: Included with retail copies, containing backstory and instructions3
  • Box Insert: Featured the dystopian narrative setup for the Earth Federation conflict5

Critical Perspective

Threshold occupies an interesting position in Sierra’s history as a representative of the company’s early, pre-adventure game focus. While On-Line Systems would become famous for the King’s Quest series and other narrative adventures, their early catalog included numerous action titles like Threshold that helped establish the company financially. The game demonstrates competent execution of the fixed shooter formula with some innovative resource management elements.

From a historical standpoint, Threshold reflects the Wild West nature of early 1980s game development, where inspiration from arcade hits was common and expected. Warren Schwader’s decision to “take the concept and run with it” rather than create a direct clone showed creative ambition, even if the final product remained clearly derivative of Astro Blaster. The game’s commercial success helped fund On-Line Systems’ growth during a crucial period, contributing indirectly to the adventure game revolution that would follow.

Downloads

Download / Preservation

Manuals & Extras

References

Footnotes

  1. MobyGames – Threshold – release dates, platforms, publishers, ratings, technical specifications ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8 ↩9 ↩10 ↩11 ↩12 ↩13 ↩14 ↩15

  2. Wikipedia – Threshold (1981 video game) – development history, sales figures, awards, designer quotes ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8 ↩9 ↩10 ↩11 ↩12 ↩13 ↩14 ↩15 ↩16

  3. Sierra Chest – Threshold – game description, backstory, designers, engine information ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8 ↩9

  4. Internet Archive – Atari 8-bit Version – gameplay mechanics, fuel and heat systems ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8 ↩9 ↩10

  5. Games Database – Atari 2600 – official game description, enemy forces, publisher ↩ ↩2 ↩3 ↩4 ↩5

  6. RetroGames.cz – warp drive mechanic, game size, development credits ↩ ↩2

  7. My Abandonware – Threshold – user ratings, platform file sizes, user comments ↩ ↩2 ↩3 ↩4

  8. ColecoVision Addict – ROM size, rarity ratings, MD5 hash ↩ ↩2

  9. Dynamix Fandom – Sierra Entertainment – company history, founding information ↩ ↩2

  10. Wikipedia – List of Sierra Entertainment video games – specific platform release dates ↩ ↩2

  11. Internet Archive – Apple II Version – preservation, file information ↩

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