It’s because of that cognitive science brain stuff again. By putting in a small amount of randomization, we can keep the averages within a mathematically predictable range, but still set up situations where the player cannot always perfectly predict the outcome of an event. This puts the player into a state of suspense and tension at being unable to predict the answer to the question “will this work?” The amount of tension is directly proportional to how important the result is. Player brains anticipate the result but can’t know it. That anticipation makes the payoff feel bigger and better.

This can add frustration when the player’s chance of failure is small but occasionally happens (e.g. 5% chance to miss), but that’s also balanced by the sense of exhilaration players get when things are unlikely to work but still do in a clutch situation. It’s also the same reason that we don’t make all loot purchaseable via earned game currency. Players get that extra shot of exhilaration when something they can’t just buy (but really wanted) drops.

When you can predict exactly what’s going to happen, there’s no anticipation and no “story” - everything goes exactly as planned. Perfectly predictable events can grow dull over time, which is not super good for game longevity. That question of “will this work?” adds a lot of emotional reaction (via anticipation) to many in-game situations. We all have a story about playing a game where we managed to squeak out a win when we thought we were going to lose. If games had only perfect prediction, those situations could never happen and I think the player experience would be much worse for it. 

The FANTa Project is currently on hiatus while I am crunching at work too busy.

[What is the FANTa project?] [Git the FANTa Project]

Got a burning question you want answered?

• Short questions: Ask a Game Dev on Twitter
• Long questions: Ask a Game Dev on Tumblr
• Frequent Questions: The FAQ