Yahtzee is played like the standard dice game and has the same simple rules. The game can be played by 1 or 2 players. Once the five dice are rolled, the player has the option to re-roll any of the dice to improve his lot. The player then selects which category to apply the dice combinations toward. There are several categories that must be filled. Of course, rolling all dice with the same number provides a Yahtzee. The player attempts to get the highest score possible for the Upper Total of rolls, which consists of getting 1-of-a-kind rolls of the 6 different dice face possibilities. The Lower Total consists of combinations that are similar to a poker hand. At the end of the game the Upper Total and Lower Total are added together to provide the final score.
This is a very simple game, which is only text based. The dice and pointers to the dice and options are Player/Missile graphics, but everything else is rendered in BASIC Graphics 0 mode, which is 40 characters x 24 rows. A simple graphic representation of “Professor Yahtzee” is provided using standard Atari character graphics.
Eric wrote this game by himself in his senior year of college (1987). The dice are made up of a Player/Missile graphic, and actually uses a character string to hold the graphics. Character Strings in ATARI BASIC had several functions for moving parts of strings around, and these functions were done in very fast Assembly language. Eric took advantage of these string manipulation functions to quickly change the characters in the dice.
This was the second to last game ever written, just before Sokoban.