Threshold_XEROX Commodore 64 game

Threshold is a space-themed fixed shooter created by Warren Schwader and Ken Williams for the Apple II, published by On-Line Systems in 1981. Inspired by Sega's Astro Blaster arcade video game, the game introduces various enemy ship types and wave formations as players progress. Reviewers noted that this diversity set Threshold apart from many similar shoot 'em up games.

The game, which sold approximately 25,000 copies, was ported to different systems via ROM cartridge releases. These included the Atari 8-bit family and VIC-20 in 1981, Commodore 64 in 1983, and ColecoVision and Thomson computers in 1984. Tigervision published an adaptation for the Atari 2600 in 1982.

In Threshold, players control the spaceship "Threshold," utilizing its laser weapon to eliminate waves of alien attackers. Similar to Astro Blaster, firing the laser increases its temperature, requiring it to cool down when not in use. If the temperature bar fills completely, the weapon becomes temporarily unusable. Once per ship, pulling back on the joystick activates a "warp drive," briefly slowing down the action.

The game's inspiration came from Ken Williams playing an Astro Blaster arcade machine and calling Warren Schwader. According to Schwader, instead of replicating the game in detail, they aimed to capture the same experience for Threshold players. The development took two months, with Williams contributing to the project for two weeks, focusing on writing the Apple II animation routines.

Threshold received positive reviews, with critics praising its animation, variety of enemy types, and waves. The Atari 2600 port by Tigervision earned a "Certificate of Merit" in the "Best Science Fiction/Fantasy Videogame" category of the 1983 Arcade Awards.

Reviewers highlighted the superb animation in the Apple II version, emphasizing the game's depth and variety. Some criticism included occasional confusion between stars in the animated background and enemy bullets. Electronic Games commended the graphics in the Atari 8-bit computer version but noted occasional loading between levels and an overall high difficulty level.