Making Games With PPB

we got our next knock up Piper Buster is gonna tell us about games let's see the round of applause to fight all right so specifically we're going to talk about making games with ppb which most of you probably haven't heard of yet so I'm hiper Sundstrom I'm a software engineer at a company called GLG I've mostly do web development and database program I'm also a community organizer in the New York City Python area Python community and I'm also the author of PDB which is again why you probably haven't heard of it yet if you want to follow me or tweet about this at PA sundström and app pursuit pie bear so what is ppb oh this is did not work on this screen oh okay so BBB we are an open source idiomatic Python event-driven education focused game library lots and lots of words to apply to one resource we're gonna kind of take them in order I don't think I have to explain open source to this room but I do to others so that's why it's there when I say idiomatic Python what I mean is the code you write with ppb looks and feels like Python by event-driven I mean that you write your code as responses to events and not as a game loop like you're probably used to if you've done game programming and by education focused I mean that primarily when I need to make a decision on what of three different engineering options do we need to do I go and talk to a bunch of teachers uh-huh so that's what PPP is this is the team I am my career at the top I'm PA comes from on github I am the API author and basically the manager of the project jamie is my co maintainer jamie is the actual one who is actually the one who wrote the event system and has done a lot of great work and is currently trying to get an animation framework over the line and Nicko has done a out of work on making our numbers stuff all work better clearly not the person to talk about it um so let's Wow that is the wrong file to open this is why you don't like good folks all right so let's actually talk about making games when important about this talk I'm not gonna really cover these basics in a lot of detail this is just a very quick primer if you want more I've given as hard on making games the actual concepts you can find them on YouTube under my name so all games at their core have an event loop we actually call this a couple of different things depending on who's talking about it sometimes they're called render loop sometimes their game loops sometimes their simulation loops they all kind of tell you what's going on under the hood we want to respond to events update the simulation and then render usually in that order but it doesn't actually matter that much so in ppb though you don't have to write this from loop anymore we make it as easy as possible to get your first loop going so there we go we have a window open two lines of code if anyone's ever played with the other libraries this is a little more less than you have to do there um so this is just again the basic everything needs a loop here's how we handle it but let's talk about events events are the things that a lot of people have a little trouble wrapping their minds around so what are events anyway events are things like mouse motion the window trying to close the update event in our case in general we also can use this for like message passing so that different objects can talk to each other MPP B we have built the API so that it's fairly simple to write new event handlers so here we're gonna respond to key presses how did to do so we have a bunch of constants defining all of the various keys which is what you saw pop up there and when I press the spacebar we're going to just increase the size of the object so we do this every time I press space it grows so that's how simple it is to actually write your event handlers we have these four Mouse motion we have them four there's an update event and a couple of other features this is basically where all of your actual game logic is going to live is inside your game objects inside event handlers so let's talk about rendering I'm sure you've noticed that we already do a lot of rendering for you but we're gonna demo some other stuff instead so when we're talking graphics as far as ppb is concerned we do raster graphics it's a 2d context we're using actual pixel arrays under the hood but mostly you don't actually have to think about this we would rather you worry about the metadata and not the actual process of rendering so as you've seen a couple of times already you know week we get a square for free doesn't take much effort that's just the base right there but you can also do things like add images this all right so we run this oh wait let me uncomment here we go all right so now we have a ship on screen that's all it took other features you can do just using metadata in the same way you've kind of already seen this but we'll do it again and you can also manipulate the rotation and so now we have a bigger one and a reversed one and then additionally we've made the all of these features composite able so we can do all the things with basically no extra code so renderings nice and easy you can manipulate all of those values as much as you want so let's move on to the actual architecture of how goo PV works and then we'll get into the actual fun stuff so we actually start at the top of our tree this line of code is ugly and there's a reason we hide it behind ppb run so this is basically how you set up your own custom engine normally inside the context manager we would call a game engine dot run but I'm actually trying to show you some things so we're not doing that here inside the engine though there is a set of subsystems subsystems are actually okay so these subsystems are actually how we manage adding new features to the game engine primarily they were designed this way so that it made it really easy for the developers to do this but it also adds an API so that if you want to add manipulations of how the engine works you can add them to this list and then once we start the engine because it kind of does some lazy work once you start it you also have a whoa that is the wrong file here we go all right so if you look down at the bottom here there is a list of scenes right now there's only one because we haven't done anything with them we keep them in a list but we're using it as a stack so you can push pop and replace and to assist when that we actually have this game engine current scene which gives us whatever's on top of the staff nice and easy the neat thing about our scenes though is they're actually containers so they're iterable oh right can't remove that so we do this and as you can see we now have a object that has two different objects inside of it this is just a list because it's nicer to print so the engine uses events to manage them and I'll cover that in detail since that's one of the advanced features and then sprites what the things inside are basically just data bags as I kind of just demonstrated that you can attach event handlers to in this file I've done that up here just so that the sprite actually responds to the update event in the moment all right so the engine is actually also how we publish events under the hood we you can send up a signal so if you saw that signal function and the parameters a bit ago it's just a function on the engine we can print the events just to show what's there all right so there is a DQ underneath death whatever I can never remember how to pronounce it and then if we call publish it should it did not go through I have to figure that out later Oh in general though when you do GE publish every object is actually going to receive that event and it works when you're actually running the engine I don't know why it's not working here oh all right so that is that's the boring stuff this is the background information you need to be able to understand what's going on so let's actually talk about making the actual games themselves just close all this down so we've talked about system events that kind of covered the kinds of things that are in them but as I mentioned what about manipulating them ourselves that signal function we have here what we're going to do is have this ship which currently does this look wrong file so this is what you've got so far what we're going to actually do is make it so that one of those two ships actually sends another update event every time so signal so here's that actual update event and we're going to use the existing ones time Delta before I actually blow this up because I have done it multiple times already right so if we run this you saw about how fast it was going they should go about twice as fast so that's one way you can do it you can signal any of the existing events by doing this this is less useful for actually making games but it's good if you need to do things like faking player input so you can make your own classes just using data classes actually so here we have a data class on time dilation of basically the goal here is we're going to instead of responding to update events we're going to have the time dilation ship change how often it responds so we put our code here soft accumulator plus equals self dot speed Wow [Music] it's greater than or equal to one so we can just raise our event and this needed a time Delta as well so we want to keep it the same and then down here you have on time dilation is where we actually do the movement so if I run this now it'll break wonderful I think it's this this is causing the weird interaction so this should is not doing the thing this is why you don't like code oh yes I did I I did this multiple times while practicing and reminding myself not to do it there we go now I should just work so right now it's actually moving the same speed because down here where we've been San Shi edit it we've made speed one but let's make speed whoa 13 it would go very fast oh and there we've made it faster it's running on the same update speed as everything else but it's not changing its speed it's actually updating more times so the other cool thing you can do actually do is extending events um you could do let's see right pebble eater so I need to comment this out because I don't want two engines running at once mostly they won't run at once so we write a little function up the file we have a global called leader that gets set during the set up and we call GE dot run and up here we're going to just print I missed a step here so here we go we have to GE dot register we are going to respond to the update event and then our callback is add leader so now despite it not being defined normally you'll see that every time there's an update event we've been getting output of what's on that leader so this is one way you can make objects available to other things is by registering one of these callbacks to add a new object to each event that you care about so that's events what about scenes I mentioned changing scenes this is really just how you manage the state machine that is the staff so in this example we have a slash thing I am going to warn this is going to flash a little bit for anyone who might have problems with that so to start with we just signal a start scene with our new game screen and this fun bug this isn't actually gonna do anything but it will not try to instantiate the scene without it we're working on that all right so if we run this now we should have it'll go from one to another okay so that was the start scene in the middle of that what you're going to get is the splash screen here will actually receive a on pause event just to demo this so we run this and so winix color changed the splash was paused every scene when it gets started actually receives a on scene started which will see the function of in just a moment so when we're done with the game screen we're actually gonna move to this game over screen and we have replaced scene for that same idea we just pass it our new scene and the quarks all right so there's that so this is going to last for about a second and then it's going to switch to the game over screen when it stops it's actually going to print the runtime so you can actually see some of the other features here all right so we do this we get this then this then this will close this and as you can see when the first scene pause we have that when the game tie game started we saved that start time and then when it stops we actually printed the actual runtime which is about a second and then the last thing we need to do is be able to get back to that initial scene that's all still on the staff that one's even easier we just need to tell it to stop the scene this one doesn't have any examples but it should turn back to that initial purple color when we're done oh it helps to actually spell my libraries correctly so that's basically all you need to know to start manipulating scenes when you start working with scenes just consider them a piece of the game from levels to splash strings to scoring screens to main menus things like that and so you just use that state machine to move between them next tool you need to know how to use sprites so you've seen sprites being used through all of these examples that are like the core thing that puts things on screen this is actually going to be about how to make those sprites interact with each other so the first thing we can actually do is we can act their Python classes we can pass other sprites as parameters so in this sample we're going to here's our leader seemed to add our leader so here's this just the same thing here what seriously all right so we've done this so this is going to put two three objects on screen and then if we look at the code on app on update the leader is going to basically move nowhere because it doesn't have a target all right no right it's going to move towards the center of the screen and then the other ones are going to try to follow the leader which is basically what we get so that was just using parameters you just pass things around like you would any other Python code but you can also use scene get so what we're actually gonna do now is we're gonna add a player and just so I can demo some stuff that's gonna crash you want a list of hashable x' and not a strength oh so we're gonna have this player if I run this as you can see the player is going to follow the mouse so that's done and so here instead of going to this we need an update scene so just like I mentioned earlier where where you can extend the event system the engine does its itself so that the current scene is always available on every single event you see so in epic a team gets so the first thing we can do is look by Kimes and this is just gonna find everything of that type and target is going to be player top position so what this should do is as it moves around the leader is going to start following the player so another simple way to do this in addition you don't have to use kinds there's also by tag which this should work exactly the same way oh I should change that to the actual thing we're looking for so you can use that tag system to also grab objects so if you have multiple different types under the same tag you'll get all of them and then the last thing you can do is actually just use the messaging system I don't actually have a sample ready for this but you've kind of seen this all in order so what we'll do is [Music] we need data classes all right so we've all seen this so what we're going to do in here this will actually go signal target move and it will be that player dot position and then down here or we know if self-talk leader yep this is a little backwards leader here is not a boolean it's the actual leader itself so I have to do all my logic in Reverse so if we're not the leader we're actually going to care more about this target move so this will be self dot target equals event dot position and then up here okay so now instead of following the leader itself it's going to go where the leader tells it to right here we go okay well like I said I didn't prep this one I'm not sure what's wrong here it's not callable do I try to call a okay so we're gonna move on but that is basically how it would work if I can figure out where I'm trying to do that oh wow that that's it's right here hey there we go and now they're all mostly chasing the player so yeah there's the various ways you can actually put sprites together to do things together three different systems you'll use them for different things generally it depends on what information you have at the time on which one you're going to want to make so the last step well let's talk about subsystems so I mentioned subsystems is how we actually add features to the engine so I am actually going to build an achievement system right here in front of you remarkably it's more simple than you think so this is what it looks like so we just have a very loose game here all right so in order to get this started the first thing we're actually going to need is to start building let me delete that one minute okay I might not be able to get this done all right so the basic idea is you would make your you do this all subsystems have to take args and kwargs because they kind of receive they're gonna receive all of the quarks for all of the subsystems that's just how things in instantiate goal equals 10 I'm not gonna get to show this one running but basically you would write an event that is the progress when you get that self dot count plus equals one this self goal if goal is greater than count or reverse that all right raise an event and then a sprite can be created which you see somewhere no I didn't write that part okay yeah you would just raise an event and then can create a sprite in response to that event on the scene and you'd have a working achievement system [Applause]