In Catch 23 the player is parachuted above an island, containing a test development site. His mission is to find the CK23, an enemy weapon. Once found the player must steal the design and set off a nuclear bomb that will destroy the island. It's 22:00 when parachuted and the sun rises at 6:00, meaning the player has a full day (/night) work to circumvent enemy patrols, search houses for additional weapons and explosives, navigate the terrain, fences etc and reach his destination, hopefully without setting of an alarm For that end, the player has a dangerometer. Set off an alarm and the dangerometer will show an increased value. And indeed, enemy soldiers will rush to the explosion to investigate.
Enemy vehicles can be circumvented, but it's hard to avoid the foot patrols, which must be dealt with by swift and accurate gunfights.
The game uses vector graphics.