Warren Robinett‘s early videogame Adventure for the 2600 is mostly remembered for including the first known easter egg, and indeed was the example that caused the term to be coined in the first place. Adventure was a remarkable achievement by any standard, but especially for a platform with 4kb of ROM and 128 bytes of RAM.
One of Adventure‘s signature characters was the Bat, and the Bat was both elegant in its simplicity and awesome in its impact. In short, the bat would fly randomly through the game’s screens and would pick up and drop items. The bat’s movement and item actions were simulated even when the bat was off screen, meaning that while you traversed the world the bat was always out there doing its thing. (By contrast, the dragons only did two things: charge you when they see you and try to kill you, and run from you if you had the sword.)
Besides being an autonomous and persistent actor whose behavior was highly randomized, the bat had two unusual abilities:
- When it arrived on the same screen as you, the bat could choose to steal the item you were currently carrying and drop whatever item it previously had in its place.
- The bat not only could pick up and drop items, it could also pick up and drop dragons.
With this basket of behaviors, the bat was a true agent of chaos who was neither your enemy or your ally. And its unpredictability and broad freedom to act resulted in a variety of delightful procedural outcomes:
- You are looking for a crucial item. The bat flies by carrying exactly what you need. Argh!
- You are carrying a crucial item. The bat steals it from you and leaves behind something useless. Argh!
- You are carrying an item. The bat flies by with a better item and swaps it with you. But the item she drops is on the other side of a wall because you’re in a maze. Argh!
- You are running from a dragon. The bat picks up the dragon and flies away with it. Yay!
- You are in the invisible maze with the sword. The bat enters carrying a dragon. The bat takes your sword and leaves you with the dragon and you now have to escape the dragon within the maze. Argh!
- You are running from a dragon. The bat flies in carrying the sword and flies over the dragon. The sword kills the dragon. Yay!
This, of course, repeats, and to be clear none of the above examples were deliberately coded scenarios. They simply arose naturally out of the behaviors.
The combinatorial outcome of items, locations, player goals, and creature behaviors resulted in a highly replayable experience that could repeatedly surprise, delight, and aggravate you. Adventure was a fun and innovative game, but the bat is what pushed its gameplay over the top.