Aspects of playing
by The Sheep
Four aspects of playing a computer game
There are four things we look for in the games we play. Every game will give us a mix of those four, a mix of unequal proportions.
Play as in playing chess or poker
The computer game may be viewed as 'game' in it's common sense, with it's strict rules, a board, tokens, etc. Sometimes it will require thinking, sometimes just luck (and sometimes good reflexes), but those can be very abstract. It's important to remember that every computer game is a game first. In order to play such a game, first of all you have to know and comprehend it's rules. There may be hidden information or gambling, but still the player should have enough information to make decisions. The overall looks of the game isn't really important, as long as it's not interfering with the players view -- as long, as the board is visible, the tokens are distinguishable, and the cards aren't until they are face up.
Play as in playing dolls
This is so called role-playing. It's no longer a game -- it's a world, in which the players can operate using their characters as proxies. Many games skip this aspect entirely, but it's a strong part of roguelikes, so it would be unwise to leave it. What do you need for role-playing? Not much, really. A setting, a background story, some descriptions, some concept art, rules resembling those of the Real World. But there are things that stand in the way. Too much detail, to narrow path will kill the role-playing, break the suspension of disbelief. Look at the kid's dolls -- they are not realistic, even Barbie isn't. The important parts are exaggerated, everything else is left for user's imagination. The books tend to be more immersive than movies -- it's important to remember that.
Play as in watching a play
Ok, this metaphor is a little stretched. It should be rather like watching a movie. Yes, there's still some immersion, one might even make several decisions, but what one is most concerned about is just watching. One may watch because what he sees is beautifully drawn, nicely animated, perfectly calculated, but one might also watch because the story is entertaining, the characters are cute, the narration is atmospheric or one just wants to know what will happen next. Modern games go mostly in this direction, but there's not much place for it in a roguelike game. Yes, one can explore nicely-generated dungeon, be interested when he finds certain item for the first time, feel emotions when he completes certain quest for the first time. But that's it.
Play as in playing sports
A competition. The simple satisfaction of winning, or the more complicated triumph of being better than ones friends. The games that aim at delivering this must be challenging. Also, some mechanisms that will allow to compare scores will help. A winning condition is an absolute minimum. Additional challenges, like ironman mode can help here too.
Those four won't cover everything the game might offer. There are educational games, that will teach something. There are construction games that will give the joy of creating. There are trading games, that will allow to exchange goods with friends. But those 4 elements seem to be the most common.