Critical Mass

Critical Mass is a sci-fi action game set on a distant asteroid. An anti-matter conversion plant has been captured by hostile aliens. The invaders threaten to overload the reactor, creating a black hole that would destroy the planetary system unless Earth surrenders. Your mission: travel across the asteroid's surface, infiltrate enemy positions, and disable the converter before it reaches critical mass. Control a rocket-propelled hovercraft equipped with a laser and force field. Collisions drain energy. If destroyed, you eject with a jetpack and must find a new ship while avoiding deadly sandworms. Eight zones to traverse before reaching the heavily fortified power plant.

ZX Spectrum

Released in 1985 by Durell Software, developed by Simon Francis with additional work by Julian Breeze . The ZX Spectrum version features an isometric desert landscape rendered with more realistic colours and depth than the Amstrad CPC conversion, according to contemporary reviews . The hovercraft controls utilise vectored movement—push forward to accelerate, pull back to decrease speed—making ship handling a deliberate challenge . Computer Gamer magazine gave the game an excellent review, describing it as "an excellent arcade game that will challenge the best" . The five-zone gauntlet culminates in a wall that must be breached by blasting a hole, with alien defences rushing to push you away before the wall regenerates. After completing the mission, higher difficulty levels become available. An acclaimed Spectrum title that remains playable and challenging today.