Playing a time traveller, "Time Master Tim," the player's objective is to collect dinosaur eggs and rescue hatchling dinosaurs while avoiding snakes ("proto-snakes"), gigantic spiders ("proto-spiders"), flying creatures ("proto-pedes"), and the dinosaurs' mother (or "Dino Mom").

Physical contact with any creature will cause the player to be contaminated, and the player will experience "devolution" into a prehistoric spider (as a result of "contamination"), and lose a life, unless the player returns to the "time warp" transport force field before a de-evolution timer runs out. Contamination also destroys eggs and hatchling dinosaurs on contact, reducing the player's score. While within the transport force field, Tim is safe from all creatures except the Dino Mom.