Similarly, it is not necessarily "hiding" the rules when one has experience points, algorithms for damage, etc, in adventure games. It is the introduction of random chance, which is common in a vast number of games, especially those of the board game variety. For instance, when playing Monopoly, one would not expect to know the exact dice roll they will have in a game, or the property they will have the chance to acquire. The player simply knows the parameters possible (I will be able to move between 1 and 12 spaces when I roll this dice, and the set of possible results of the spaces I land on within those 12 moves is clear). Thinking of the possible outcomes of the dice roll as a (very simple) algorithm makes it very similar to the "rolls" done by computers in adventure games. The main difference is that most people don't want to get out their calculators for Monopoly (alright, take my dice roll times 5, subtract 3, mod it with 3, and... ooh. Baltic Avenue.) while in computer games relatively complex arithmetic is no problem whatsoever.