All language subtitles for 1. General Concepts

What are finite state machines?
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Well, a finite state machine or, for short, FSM is a collection of states and transitions.
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The states represent the actions that an AI agent can take. For example: fire, run, patrol, and so on, so
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forth.
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And the transitions are the links between these actions that tells when the AI should change its current
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state.
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For example, if the AI was patrolling and it encounters a player, then the state should change from
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patrol to attack so that AI can properly play the animation, fire the projectile and face and run
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towards the enemy.
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This is one example, but finite state machines is one of the most common ways to implement AI
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in games.
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Behind the scenes, an FSM is basically a graph and if you don't know what the graph is, then you should
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definitely check the bonus section, the data structures.
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What it does is basically these nodes represent the states and the transitions represent the edges between
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them.
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Let's now look at the pros and cons of using a finite state machine.
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Well, one of the most important pros is the fact that it's very easy to use and understand.
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You basically create the states.
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You name them and you use them.
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You connect them via transitions.
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And basically, this is it.
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And of course, because of its simplicity, that means that it's very fast.
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So if you have a lot of AI instances, for example: 1000, then a finite state machine would do good
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because it doesn't require so much processing power.
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What are the cons of a finite state machine?
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Well, the first one that it might get out of hand quickly if you had more states, more transitions,
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you interconnect them with each other, then you might end up with a spaghetti of something that it's
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hard to maintain.
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And it's also hard to reuse because you cannot just take parts out of it because they are tightly connected
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with each other.
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But with all of these cons, I still believe it's a powerful system and it's used in modern games.
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There are ways to mitigate all of these risks by implementing something called hierarchical state machines.
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And the good news is that in the final project that we will have in this course, we actually have a
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hierarchical finite state machine.
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Basically what it means is that the groups states together in bigger states to avoid having too many
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redundant transitions.
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But you'll find out more in the later project. Now that you know what the final state machine is
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let's find out how you can implement one yourself in Godot.