Tag: item drop

Stat-Driven Causality: Better than pseudo-randomness!

Watch this video on how the “random” loot drops in the original Legend of Zelda were actually determined:

I found it very interesting. In my game projects, one of the more difficult areas of game design is getting the frequency of the loot drops to feel right.

Let’s look at the ways in which the loot drops in Zelda are not random.

  1. Loot drops happen because of an event, eg defeating an enemy. They don’t happen “randomly” for no apparent reason. This drives a feedback loop of “kill monster, get treasure”.
  2. Which type of item gets dropped is actually not random. However, it’s important for the drop to seem random to the player, so they never can be sure of what they’re going to get. This keeps them guessing and curious: “What will I get if I kill this monster? There’s only one way to find out; better kill it!” invites play much more than “Ho hum, here’s another [enemy]; I know they only drop [type], and I don’t need that right now, so I’ll just walk by it.”
  3. It does seem that certain types of enemies do drop certain types of loot a bit more often. For example, in the overworld Tektites seem to be pretty reliable about dropping rupees, and tend to yield a higher proportion of blue rupees that are worth 5. They do drop other things, bombs and hearts, and fairies, but it does seem like they will drop rupees a bit more than other types of enemies. There may be a similar relationship between other types of enemies and other types of loot. This gives certain areas of the map, where these types of enemies appear, have strategic value for “farming” a given type of resource.
  4. It would make sense that more challenging enemies might yield more/better loot, but I don’t notice this so much when I play LoZ. It seems that as you progress through the game, the difficulty of the monsters ramps up, matching your own power increase, but that the reward remains more or less constant. Still, in many games, there’s a directly relationship between challenge and reward.
  5. By connecting the frequency and type of loot dropped to a complex conditional based on the internal state of the game’s various counts, it’s possible to tune the difficulty of the game to a far more precise degree than could be done through purely random loot drops. For example, if the player is low on hearts, you could use that data to drive a slight increase in the amount of health drops, to make the game easier. Or, to make the game more challenging, you could make health drops rarer when you’re low. This can be tweaked so that “easier” areas of the game have the more generous/forgiving drop rate, while the harder areas have stingy/unforgiving drop rates.

Up until now, I have thought of loot drops as something based on completely random chance, not influenced by various factors being tracked in the game. I had played with various stochastic functions to create what felt like “right” odds to give the game the right “feel”, and wondered why simple random distribution never felt quite right.

But what is “right” is highly subjective, difficult to define, and requires extensive time spent playtesting in order to gauge “feel”. But now, I see a much more interesting potential in tying the frequency and/or item dropped to causal relationships to various stat counters. What’s great about tying the loot drops to in-game stats is that it allows you to directly apply mechanisms to balance the game, based on how the stats reflect the player’s performance, their progress in the game, and the amount of difficulty you want at that point in the game.

Exactly how to do this will still be very subjective, and require extensive play testing, of course, but it will be tune-able and in the control of the developer, rather than purely random chance. I am excited by the possibility of using the stats model to drive feedback loops which can help to govern the game’s challenge level, or to provide certain items when they are more likely to be needed, or just to make the loot drop frequencies seem a little more interesting and less totally random. It seems like a potentially much more elegant way of distributing items in the game.