An action game set at a time when nascent, insectoid life forms battled each other for survival and for domination of the ecosystem, in an ancient epoch at the dawn of life on Earth (or thereabouts). The player, cast in the role of a scorpion, is tasked with overcoming an incursion by a particularly mean strain of killer spiders. Similar to Tempest, the player patrols the top edge of a tunnel seen from a bird's-eye view, as enemies rise up from the depths. Firing volleys of venom will destroy the unwelcome arachnids as they try to scale the walls, if they manage to crawl their way to the top, they open holes in the tunnel wall (which spell death for the player). Each wave of attack adds an intermediate platform within the tunnel, which the spiders can move along, change directions and dodge the player's fire. Also traveling along the top edge is a special color-changing brick: one color means instant death for the player, the other can be picked up, which increases the score multiplier, acts as a shield and allows the player to fix broken sections of the tunnel wall. Good aim is encouraged - extra lives may be gained by keeping a high percentage of hits.