Warren Robinett, the veteran programmer, designer and The Learning Company founder known for his groundbreaking game design work at Atari, TLC and NASA, is coming to GDC 2015 to deliver a Classic Game Postmortem on the creation of his hit 1979 game Adventure for the Atari 2600 console. Adventure is particularly notable for (among other things) being one of the first graphical action-adventure games ever released. Adventure also contained one of the earliest known "Easter eggs" ever hidden in a game by a designer -- in this case, a hidden screen revealing Robinett's name and authorship at a time when Atari was unwilling to publicly credit game makers for their work. Thus his efforts to create Adventure meaningfully advanced both the practice of game development and the fight for developers to be recognized for their work. The talk is about the implementation of Adventure. For clarity, the game code has been translated into C (from its original 6502 assembler code). Because memory was extremely expensive in the late 70's, the program for Adventure had to fit into a 4K-byte ROM chip. Therefore the program was very short -- barely a dozen pages of C code. The game had 30 rooms, and 18 objects of 12 different types -- the square Man (the player's avatar), the Chalice (the Grail-like goal of the game), 3 castles with matching keys to open them, 3 dragons and a sword to kill them, a bat that flew in and stole your stuff, a magnet that attracted things, several mazes and a bridge that let you cross its walls. How was all this jammed into 4K? A good data structure was the heart of the game: the room-list and object-list. There was also a very effective "Behavioristic" scheme for giving "desires" and "fears" to the creatures in the game (which caused them to flee from or pursue certain other objects). For more implementation details, see the E-book "The Annotated Adventure" (warrenrobinett.com/adventure). Within this highly-compressed code can be seen the skeleton of the modern adventure game, boiled down to its essentials.