I'm not pointing this out to be pedantic, I promise, but what you've called a behavior tree is a hierarchical state machine. A behavior tree is a fundamentally very different approach to a logic control structure. The ONLY reason I point this out is because you have an audience of new developers and this could cause a lot of confusion over time as this misunderstanding propagates outward and with state machines and behavior trees both being fundamental approaches to game AI. Similar to the way Roblox kids call incremental/idle games "simulators", which are something else entirely, or how so many younger people say "literally" when they mean "figuratively". It creates a communication barrier between two generations that makes it more difficult for lessons to be passed down. New devs have to fight through a lot of confusion and endure a lot of frustration in their journey to becoming intermediate devs and these kinds of misunderstandings can make the harder parts of the learning curve even harder. The misnomer aside, you did an excellent job of communicating some useful concepts that are usually hard earned through experience and that's very difficult to do well. I sincerely hope you keep making content like this because you're an excellent communicator and we really don't have enough of those in the world.

This coding style is one I've gradually moved towards over time. I didn't realize it until watching this. I always thought I was using inheritance, but it turns out I was employing a hybrid approach. I use this method when writing full-stack programs, and it has saved me so much trouble because it's easier to swap out modules and functions without breaking everything.

Whatching that video feels like sitting at some jazz cafe in a noir detective movie

The problem with inheritance is not necessarily itself, but the fact that people use it in places that they are not supposed to. It is a principle like any other in software development/computer science, and like any other principle, you need to think about if, and how you should implement it. Its common use probably stems from the fact that it gets taught the earliest in university/courses, and alternatives are taught either later or not at all. A different way to mitigate the problems that you referenced is the decorator pattern, but I would not recommend it, since it can get overly complicated quick, especially if there is a lot of divergence between the classes that exist. I am currently not involved in any projects that would need OOP principles, but if I find myself in a situation like that in the future, I will give it a try. I enjoyed the video, good job. The editing is really good.

I really appreciate your explanation, Nesi. This is exactly why I dropped modding ArmA 3 and decided to just make my own damn game with Godot. Everything custom in A3's config scripting inherits from base classes at the top of the game asset inheritance tree, which results in having to redefine or add unnecessary lines to turn off certain features to each custom class, while the original class is still technically the overriding class, meaning to add new stuff you have to inherit from the base class all of its code, and if you want to change anything in your custom class at the bottom you usually have to hunt down and modify lines that pertain to what you want to change. In this example of a state machine, you can not only pick and choose what to inherit from but you're not stuck with pre-packaged components you might not even use. It's just smarter and more efficient to work with.

Hey congrats on tackling that tech debt. It always surprises me that no matter how long I've been coding I always accumulate tech debt like this and have to go back to refactor it.

As an OOP pilled dev, the randomize function seems like an oversight in the first place. That sort of manipulation of variables upon creation of the object would be better done in the constructor method. You can have as many constructors with different method signatures as you want. Usually, for this sort of operation, you would have a blank constructor, say, titan(). This would initialize the object, and you could use it to set values randomly. Then you would have another constructor, say, titan(String name, int hp, int speed) and set the in scope variables using those values. There would be no need for creating subclasses.

Good video structure. I can tell you that you're a lot easier to understand than other channels I've watched on KZfaq and the reason why that is, is because when you are about to explain something you take short breaks before explaining everything and even when you do explain everything you also are taking short breaks in-between each chunk of information to let the viewers mind catch up with the information you're saying. I would say that in the future try to think of doing this more often because it really helps the viewer (me) and also, I can say that it makes you stand out as a content creator as well. Keep up the hard work Nesi. 🙏

Inheritance makes sense if you actually have shared logic, but it's easy to overuse because we have a tendency to want to create "logical" inheritance hierarchies. Having a ParticleEmitter base class the efficiently batch renders particles makes sense to me, the only reason you'd ever want to inherit from it is if you want to emit particles while for your titan example you could imagine a friendly titan that just caries you from place to place instead of attacking, in that case the inuitive thing to do is inherit from Titan, but the practical thing to do is inherit from something like Transporter or MovingPlatform

Loved this video. I've seen other explanations of behavior trees and state machines for game development that seemed to overcomplicate the communication between nodes. This was a great video!❤

Some of the best advice I've ever heard was "Favor composition over inheritance". In 30+ years of software development there have been very few times when I've found non-trivial inheritance to be of use. But I'm constantly finding composition to be useful.

Composition isn't just having a list of things on an object. Composition is inheriting multiple interfaces instead of one baseClass. So instead of Enemy : Entity. You have Enemy : ICanJump, ICanWalk, IDamagable, IHasInventory And each of those interfaces handles the default logic. Then later when you want to damage an object, you don't check if it's an Enemy, you check if it's an IsDamagable and call the object's TakeDamage method. Now anything can be IDamagable. Destructible environments, the ground, the player. It doesn't matter what, because all it's promising is that it takes damage. The code's intention is super transparent and easy to maintain. When people say use Composition over Inheritance, they mean direct inheritance. Not inheriting in general. Composition is still a type of inheritance. You just inherit components instead of one root class. If you're not using interfaces, you're not really using composition. Just Lists. Every baseClass you consider creating, instead break it down into many interfaces each responsible for a singular thought.

Thank you for sharing your ways. It is really helpful to see how people manage their structures, and yours seem not only organised, but functional

Some time ago, I read a reddit post which explained this extremely well (sadly I can't find the link, so I have to paraphrase) and it said that inheritance is basically composition but with extra features: 1. compose the supertype in the subtype, 2. automatically delegate properties and methods to the composed instance (syntax sugar: instead of having to do x.y.z you get to do x.z), 3. Make all subtype instances valid instances of the supertype from the perspective of the type checker. Interestingly, not only does inheritance often mislead new OOP programmers into the problem you described, the 3rd feature, formally called subtype polymorphism, makes a program harder to type check too in certain cases.

This is probably the best explanation and comparison of the two I've seen yet. All of only one thing is never good, but instead you mix and match them. And sometimes, as you show here, neither inheritance nor composition are the best choice and thus you go to a state machine, or in other cases some different construct, where that is most appropriate.

Using both is usually the best

Just one thing, though: composition is actually OOP (and should not be confused with ECS). It's just a different way of doing OOP. A long time ago, in the golden days of Flash games, all the tutorials were hyping OOP, but they all advised people to use "composition over inheritance". But then.... everybody used inheritance. :) There's an interesting talk by Bob Nystrom about roguelikes where he shows the benefits of OO composition too.

love these educational / devlog style of a vids

I'm an experienced software engineer and what you've created is called an HFSM: Hierarchical Finite State Machine. When you say behavior tree, especially in the context of game dev, it usually refers to a form of AI that's similar to an HFSM but is more specialized and centric around execution over time. There are lots of videos and information on it.

Glad I’m on the right track . I name them “actions” and are basically containerized behaviors. I got priorities setup as well as additive capability which I can either have the next action be the current behaviour or an addition to the current .

What a great video and well explained! Becoming more familiar with composition is fundamental for Godot devs. Plus, the delivery and composition of your video is fantastic! Keep it up! Subbed! Thank you!

This is what includes/mixins/interface Which basically is a feature set that can be added to a class, that then from that point forward I herits naturally but isn't bound or part of the hierarchy. It's the wings problem in the animal tree

Very good video that got recommended to me exactly when I needed it since im about to run into the same issues

The pattern when combining the singleton and observer patterns to manage state is called a reactive store or observable store.

Really enjoy your style of editing, keep up the grind 👍

I'm always worried about how ro format this kind of code, but it really looks so much cleaner by the end. Hope I can use this better in future projects, thank you!

Great video! Composition is definitely a far more flexible way to compose complex ideas. One small note though, that just might come across a bit confusing to people new to the ideas watching the video, Composition and OOP are not different paradigms. OOP is an umbrella term for a collection of ideas _including_ Encapsulation, Inheritance and Polymorphism. with Polymorphism (the **is a** relationship being considered the weaker of the tools relative to composition the **has a** relationship.) As a programmer myself I always love watching the way people solve problems. awesome work!

Loved the video especially the end product with the attached debugger to see state displays on the entities

This looks like fun game to play! Something about biplanes on floating bases on the sky totally sounds like my dream game when I was 10 :D I love composition so much, but I use it so much because I can't use OOP at all, I feel like I'm not a "real programmer" because everytime I have to make interfaces I make total spaghetti and I get disappointed and burned out so fast :(

My biggest issue with inheritance is that it always makes sense when you're doing it. Like, if i start writing a program from literal scratch, and i make a bunch of simple struct-like things, then eventually I'll see what they all have in common and make a base class. Then you build more and you need base classes for your base classes. Then again, and again, and again, and by the end of it i have an impenetrable layer cake a mile high of class hierarchy. AND to top it all off, i usually don't remember which base classes did what specifically, which bloats debugging time

Your video gave me some good ideas. For some reason I was trying to implement those behaviors/actions/states using events, and that let to some weird phenomenon like a character who can negate dead, dying before triggering the skill. Using states is much more sensible. Also, OOP is the paradigm, Inheritance is a property of OOP, and Composition is a pattern of OOP. You have some concepts mixed up there, but the general idea is well explained.

This is insane quality and super useful stuff! I can't believe you have only 2.5k, at least for now :) As the other guy said, I didn't know this was about Godot until I started watching. Maybe adding "Godot" somewhere in the title or thumbnail would help? Anyways, you just earned another sub. Keep the quality going!!💪

In the game engine I'm designing, I'm using a single level of inheritance event bus system by that I mean I have a base entity class of which there is a vector entities which it loops through and calls the perspective function depending on what type of event it is. [Think htmls Dom event bus] And also you have to have some sort of inheritance to properly polymorphize the container for your entities. No game engine that I know of uses truly compositional design [in fact, ECSes rely heavily on the whole polymorphism idea if I understand correctly]

This is incredibly cool! I finally feel like I understand all of it good enough to work like that on my future projects. Right now I have, weeell, I guess you could also say a mix of inheritance and composition, but in a ratio of something like 90% inheritance, 10% composition. By the way, just saying, inheritance is also valid for most projects, you can work around most problems. For example, in my game, all melee weapons a player can use actually shoot projectiles that fly really fast, but self-destruct after flying several pixels (and are invisible ofc)

Great video, keep up the good work man!

Beautiful video!

Never thought about using a behavior tree for the character I'm controlling. I did implement a behavior tree in a similar manner to this in my game though, with nodes for each behavior, and it traversing through the tree from top to bottom. Might be worth investigating for my project too..

The hardest part here is being organized and knowing how to separate the stages. Create the entire workflow and then couple each stage together.

Composition is incredibly powerful. I wrote my own set of systems using composition, ecs, state machines and archetypes. This has given me amazing versitility in writing my engine, adding to it and not even remotely worrying aboit spaghetti hierarchies, multi inheritance and many other issues that i found with oop (oop is still great) I feel that systems that find objects of certain types/composition in the project and add functionality 8s incredibly powerful. Imagine a ball, apple and wheel. They all have very different properties but all roll. Add a roll to them all and let the roll system do the rest. Just a simple example tbf.

editing is on point

Sounds kind of like bevy's ECS paradigm. I have no idea what I'm talking about though

Having well defined configuration settings can come in handy also. For example, I am working on components which require asynchronous data, so there is a use case for a separate initialization code path after construction. The options for guarding this separate execution path from user ( in this case developer ) mishandling are limited in the language I am working in. So I came up with a way to internally validate the initialization invocation, which made it possible to expose the code path, but ensure it is only being invoked internally. This also permits implementations to decide which parts of the initialization procedure they want/need for their own requirements by selectively calling up the inheritance chain. So like lazy, piece-wise configuration, similar to ad-hoc interfaces. Also kind of like an effective form of shared privacy. The language does not have built in OOP interfaces and does have private member access but not shared privacy natively.

Really enjoyed your explanation and use of examples

I clicked the video and came straight here to say THIS MAN HAS SEEN THE LIGHT AND YOU WILL TOO

The pilot freefall mechanic was pretty neat xD

Rendezook as a game mechanic is an amazing idea.

inheritance was perfect in this example if you already knew exactly what you were going to do, but it can become tricky once you start developing and coming up with new stuff. Also I get how it can become complex similarly to circular imports in python, this module needs that class and the module that defines the class needs the first module and it becomes a wooden wheel instead of a tree.

The free fall mechanic is pretty cool, not sure I’ve seen that before. Seems like you have an interesting expandable core with this approach so best of luck building on that to a more fleshed out version.

I really appreciate all the thought you've put into this video, and you make a lot of valuable observations. As someone who has been working both independently and inside the industry for 15+ years, I really have to say. None of this stuff matters. Making good games matters. I have worked so many jobs where so much stress and emphasis was put on coding paradigms. It never paid off. The engineers who wrote good code had always been that way, and the ones who wrote spaghetti had always written spaghetti. Adherence to coding paradigms and practices are born out of businesses needing to cater to a lowest common denominator. You need to focus on writing code that achieves the goal of your game. Have you seen Notch's original source code for Minecraft? It's a freaking MESS. It would make even novice coders puke. But it didn't get in the way of the game's goals, and it certainly didn't stop it from becoming the best selling game of all time.

Inheritance as well as composition have their place and often a mix is the most useful approach imo. you can have a titan that inherits from a titan base class, if there is commonly shared code between them, lets say they all have eyes and blink with them. that does not mean everything has to be shared and the different titans then even can all have their own components. Just don't overdo it with inheritance, since it becomes very confusing very quickly. Use it, if you expect to save a lot of time when changing something in the future, since you only need to change the base class(for example blink twice as fast or whatever). If you have hundrets of titans, it may save you a lot of time. If you only have 3 titans i would not bother anyway. Also in my opinion i would define the behaviour tree in your example more of a state machine - A component would be for example a damage area, that an enemy can have or not have to do damage, imo. But that beeing said, very nice to watch video, i really liked it! Good and clean presentation 👍

Any coding paradigm that you like is good to go. For me the only restriction i set is: Do not repeat yourself. If I have to update the same code in two places I better write a function or inherit it.

I have no clue what anime those „titans“ are from. But they remind me of David lewandowski‘s animations „going to the store“, „late for meeting“ and „time for sushi“ to be specific… (all on his KZfaq Page) but not a word about his work on „tron: legacy“, „oblivion“ or „top gun: maverick“

This was great! Both from a video and information perspective.

Thank you Bro! ♥

Inheritance is for interfacing. Otherwise one should compose. Change my mind.

For my non-gamedev job i use inheritance. Works, everybody knows it, wide spread.. no reason not to. For gamedev i use what's more appropriate given the situation. Usually this ends up being an inheritance focussed system with some composition. The only reason i actively switch to a different style is if the game / module is heavily performance related. In which case data oriented programming is pretty much the go-to solution. While, concept wise, data oriented programming is also very similar to composition, the core message here should be: use what's appropriate for your actual usecase. Nothing is outright better than other things. Trust me^^

My wizard for fixing codes is this process... I encounter a problem... I feed the problem to ChatGPT while thinking about it ChatGPT gives me proposals and I play around with them... I fix the problem without having to figure out where I made the problem... I ask GPT to help me revisit my problem and how to avoid it in the future... I learn and keep going...

I found myself cerrin on if my code is clear and well writen more than if it's usefull and working and this stop me from coding too long befor i actually start to make it right

Excellent explanation! These map perfectly to general software dev (though based on the way you described them I’d guess that’s your background!

Great video! I love the depth of thought put into the video and the game. Have you live streamed development? I recently started doing that and it’s really fun and all the smarty pants in the audience have helped me a lot.

such a great video! beautiful animations and pretty helpful

awesome video man, great to see stuff like this and massive luck on your game and future videos

Your randomization method is in the wrong place - you should have a spawner class which handles generating random values and instantiating titans. Data inheritance is usually stable, but logic inheritance usually indicates you’re trying to do too much in your class.

inheritance is the root of all evil

Misfired the comment button earlier and youtube edit seems broken for me. :S But I would say that composition more often refers to functional code, or maybe sometimes with OOP interfaces. I have used the *Item* -> *Tree* inheritance pattern you described though, works well. Lately though I have started using more abstract classes which actually throw if some tries to construct them directly. No doubt complexity becomes its own challenge and it depends how much you like the pain of it for the benefits you can gain.:D I start going sideways after about 4 levels deep in abstraction/hierarchies, but I have seen awesomeness at levels 5 and 6. It just depends what the use case is. I have found that the more I force myself to document closer to the root of my abstractions the more focused I am by the time I am punching out the leaf components where everything is supposed to just do what I want. Essentially, think need near the top, want at the bottom and you should do ok. :-)

The voice remind me to the Max Payne 1 cutscenes voice over 😅

awesome content

Nice explanation of composition over hesitance.

This was explained really well! Would you be able to link any of your example code or the documentation/sources that you learnt this from?

I always run into this problem. If the scope of the project is small(most are) and experimental(unique objects all over) you are better off ditching inheritance cause the busywork to get the system to adhere defeats the point of setting up inheritance (same is true with nesting). Inheritance is pretty redundant to begin with as you can just rewrite redundancies in terms of function calls fine and formulate the various types with basic if-blocks. I experimented heavily with bullet outlines across game projects, inheritance structures were never clean always dirty and a complete nightmare to edit/read/update regardless of setup. Falling back on simple principles is actually cheaper(inheritance is usually costly) and way easier to edit/organize/read: add_bullet("shotgun") function add_bullet(type) if type="shotgun" then n=10 else n=1 for i=n do add(bullets,{x=x, y=y, init=function() if type="shotgun" or "likeShotgunWithLessPellet" then dmg=5.... elseif type =...."}) You can compartmentalize everything with functions and if-blocks however you want just like could classes. It's literally the same thing as you could do in classes just you have everything together and you invoke with a single function call. The point is you don't need classes; you can generate however many bullet copies of whatever variants as desired. In regards to using classes: to solve the issues of updating I've been throwing in nested blank functions in the middle of the class's methods. So instead of rewriting the entire method for unique object or extend trees all over I can just update the tiny part. This does mean that classes who don't use it will always call a blank function, obviously not ideal to ever call blank functions, but if you calculate the alternative costs of extending all over it's usually better or irrelevant. Case usage makes every argument irrelevant though, you might have other considerations forcing traditional class outlines. Or maybe you dont need many if any unique objects and dont want to run if-blocks u dont have to...then messy class code is ideal, but can also just solve it without by making separate bullet functions (repeated code can be mitigated with functions returning functions returning the object). I like to compare most language choices to the lua one of coroutines vs switches....u can write in either to get the same job done, but you can always rewrite your coroutine code into cheaper switch code.

I get everything you said Nesi, nice video. I still need to understand what exactly is the function "set_behaviour" doing. Like how does it actually change the behavior to one of the child nodes listed in the behaviour tree?

Entertaining and educational plus clearly articulated with visuals. Holy fuck my damaged brain is in heaven for learning. 😂 BIG thankies

Hell yes just from the thumbnail. Ur on the right track.

Love this. A mix of comedy and learning. Great voice over. Keep it up! Haven't checked your channel but I'll def sub. Im interested in 2D tutorials!

It's best to use both, actually.

What did you use to edit? What did you use to create the nodes. Peak tier editing.

Everyone else: trying to understand the video and point out mistakes Me: mmm.... *Juicy montage*

Inheritance isn’t that bad when you cleverly create interfaces

The goat has uploaded 🔥

i like your video style

I use both

Great video man! I would love a deep dive on the animations you hooked into this proto. I'm having a tough time with animation/trees with Composition.

Content with style. Great video

Is your behaviour tree ,also what people also call a state machine ?

Components are great. nothing feels better than slapping some component you've made for something else onto a new object and it just *works*.

really nice graphics for the video. wow

You are ready young Padawan. Now go and watch Brian Wills why object-oriented programming is bad video.

nice video mate thanks! can you share your godot themes? loved them

Use composition and abstract.

hi, nice video, what are you using for the animations?

That code gave me chronic depression

I was taught OOP as *the* way to program at uni for years, but when I got to my gamedev spec and was given freedom to build my own project any way I see fit - I realized how easier and more maintainable things are when you use composition instead. I wasn't even looking for any alternative paradigm or anything, I was just trying to solve problems and logic always led me to structure my projects with composition.

helpful

so is every behavior just a node with a script attached to it? Looks great when it all comes together, like the labels showing the behavior

Message bus is definitely cool, but I would caution you to separate it out into multiple specialized buses. Otherwise you end up with the issue of 500 things watching the message bus and getting notified about events they don't care about which can add a lot of extra overhead and lagginess

Well, I wouldn't have the randomize() method be the constructor. I would put size, speed, etc as attributes in the constructor, and then maybe do like a check ```` if(speed == -1){ this.speed = random(0, max_val); } else { this.speed = speed; } ```` Or if you think thats too big ```` this.speed = speed == -1 ? random(0,max_val) : speed; ```` Slightly less readibale maybe, but keeps it at one line per attribute, which is nice. Use -1 when you want that attribute to be random, and the value otherwise. This also allows you to pick and choose which attributes are random.

Nice!

Lovit! My favorite puzzle I haven't solved.

I would really like to see how to get components to affect the parent. Like, if you make a Move component, how does Move change the parent’s position?

NIce