Threshold (video game)
Threshold is a space combat themed fixed shooter written by Warren Schwader and Ken Williams for the Apple II and published by On-Line Systems in 1981. Inspired by Sega's "Astro Blaster" arcade game, "Threshold" introduces many new enemy ship types and wave formations as the game progresses. Ports to other systems were all released on ROM cartridge: Atari 8-bit family and Commodore VIC-20 in 1981, Commodore 64 in 1983, and ColecoVision, Thomson computers in 1984. An Atari 2600 adaptation was published by Tigervision in 1982. Schwader also wrote the 1983 Apple II platform game  Sammy Lightfoot. Gameplay. The player controls the spaceship "Threshold", using its laser weapon to destroy waves of alien attackers. When a wave is eliminated, another appears. As in "Astro Blaster", firing the laser increases its temperature, and it cools down when not being used. If the temperature bar fills completely, then the weapon cannot be used until it fully cools. Once per ship, pulling back on the joystick activates a "warp drive" that slows the action down. Development. The game was inspired by Ken Williams playing an "Astro Blaster" arcade machine in a store and calling Warren Schwader. In  an interview in "Halcyon Days", Schwader said: It took two months to implement. Williams only worked on the project for two weeks of that time, writing the Apple II animation routines. Reception. "Threshold" sold approximately 25,000 copies. Tigervision's Atari 2600 port received a "Certificate of Merit" in the "Best Science Fiction/Fantasy Videogame" category of the 1983 Arcade Awards. Reviewing the Apple II original for "Creative Computing", David Lubar found the number of enemy types and waves to be a strong point. He wrote, "The animation in "Threshold" is superb." Giving an overall rating of "B", "The Book of  Atari Software 1983" wrote, "It's the usual scenario, with this exception: the game offers unusual depth and variety." They commented that the stars in the animated background can be misinterpreted as enemy bullets. Appraising the Atari 8-bit computer version, "Electronic Games" noticed the "Astro Blaster" connection and wrote "The graphics in "Threshold" are tremendous." The reviewer disliked the loading that occurs every so often between levels and found the game overall to be too difficult.