---
title: Building a train game with React
slug: building-a-train-game-with-react
published_at: 2020-11-02 11:37:12 +0000
updated_at: 2026-03-04 20:14:42 +0000
summary: 
description: Inspired by the coding train!
tags: []
views: 181
author: CJ Avilla
url: https://www.cjav.dev/videos/building-a-train-game-with-react
youtube_url: https://www.youtube.com/watch?v=SZuSanogjv0
youtube_id: SZuSanogjv0
embed_url: https://www.youtube.com/embed/SZuSanogjv0
thumbnail_url: https://i.ytimg.com/vi/SZuSanogjv0/hqdefault.jpg
type: video
---

# Building a train game with React

*Published: November 02, 2020*
*Views: 181*

## Watch

[Watch on YouTube](https://www.youtube.com/watch?v=SZuSanogjv0)

[![Building a train game with React](https://i.ytimg.com/vi/SZuSanogjv0/hqdefault.jpg)](https://www.youtube.com/watch?v=SZuSanogjv0)

## Description

Inspired by the coding train!

## Transcript

[Music] all right welcome back today we're hanging out and we're going to build a little uh similar to snake and we're going to use react so uh this is logie bear and he has not just logo as they see through since i'm wearing see-through since you're wearing green yes so and uh grayson do you want to introduce yourself i'm hi i'm grayson i'm also here i'm just coming in remote coming in remote so we can pair sort of repair on this and stream this remotely logan has here's here's my paper so so what we're going to do today is like so this is in the train and like in like we're gonna we're gonna actually use um emojis for this oh i have the train emoji right here all right so right here is gonna be the train emoji it spawns right here right here is where this bad guy's from and then the food will spawn at a random position i mean the luggage the luggage spawns at a random position okay so if we see right here this no this is the logging okay this is the luggage and what are these controls what are the what does that do oh those are the controls for this okay and this will respond you have to get to the luggage before this guy gets the line this is a bad guy okay okay and so is it we move the train with left right up and down do you have to like hold down the thing or do you just if you push it once does it just change direction no if you push it down it goes one it goes three pixels down three pixels down okay and then you have to push it again and then you have to push again to go three more pixels so you kind of just like tap tap tap tap tap tap to move around okay but the snake game is a little different because when you tap it you were all like [Music] okay but it is inspired by snickers it is inspired by the snake can we look at our chat instead of our brands um yeah so let's say um all right so let's switch to this view and let's make a new yeah let's make a new browser that we can look at over here and okay so the very first thing that i want to do is i think we want to we're going to make this in react today react is something that i'm excited to learn i have used it for a couple little things now but i would definitely not say that i'm like a pro at react and so when you are pro at rails oh i like i feel much more comfortable in rails than i do in in react so what we're going to do is uh create react app i heard there's a new version of create react app so we're gonna play around with that um and how does it work npx create react app my app does this does this work let's try npx create react app and we want to call it train game oh train tame no control c train game and now create react app is going to download and do a bunch of stuff uh huh oh while we're doing that let's just go to me and grayson so you can just talk for a little about downloads okay all right so so we want to get um to build so what we're trying the vlog today is what i just said and one thing i don't think anyone recognized that jerking is what this symbol is is that the sound signal yeah i i um i was at my computer and i actually caught the sound symbol oh you caught it i i like i like um i like was looking at the sound symbol and drawing it okay so um add some sound okay so what are the sounds gonna be um well we're just gonna add some mac background music that's all okay and the background music should be controllable oh it should be controllable okay why don't we start with just like what what i imagine here on this gr on this square is wow that's really hard to see okay so we're going to build a grid and see this right here yeah oh that's actually just the whole background i added um pieces out of it so i could like um so i could just write so you can add labels it's trying to add labels out of it okay so it's not really a square okay so we've got our create react app here loading up um cool all right so edit this thing save and reload okay so um okay so we've got app app.js and this instead of saying learn react we're going to say play train game and let's see if it changes play train game cool all right so then dad what we act pops up though yeah react it redirected us to react page um all right let's just say h1 like play train logo import logo oh logo what about it take away the logo okay let's do that because it's not used anymore right okay play the train game cool so now we want to make a grid of squares where i think like each each square it can be the same color as the background but that'll let us know like where on the grid the train is it's called react app yeah react app that's okay oh do you want to change the yeah we want to change the title the html title okay let's see uh title train game all right let's see boom train game how's it look good approved logan it's logia bear approved loki bear approved all right yes look grayson what's up can you just pop in that times yeah sure so what uh you disappeared i cannot hurt that's treatment to do oh yeah that's what you meant to do you meant to pop out oh okay yeah sure you're free to pop out but i meant like that sometimes so i think what we want to do is we want to render like a game here a game component i think and then i think the game component has like a board and it might have a train and it might have like a state about whether you won or you lost or maybe has the score or stuff like that and then yeah it does have a score i i just couldn't add that okay so in game.js i think we want this to be similar to well no i think we want it to be like a class component where it's like game extends react component and then we have to have a render function render and this returns like something um div and let's call this let's just say this is like the game um and then can we do that export class extends thingy and then we say like import uh game from dot slash game.js i don't know maybe that'll work um sports maybe no okay let's look it up since they're new to it since i'm new to it yeah we better look it up huh all right how do we is it module.exports equals is this all is all um is this all gonna be um like is wheels just like one of those little tab thingies and we know the rest of it um we're not using rails today we're just using yeah like like like is this is on this like rails and it's just like a little tabby and it's just like a little tab in it or is it or is it like capture all of the taps and when you don't only mean by tabs which doesn't capture all of those yeah it should capture all this all the assets and files on the left yeah so right now like when you when you load one page it's loading app.js on the index here so the index is like the entry like this is the html that we're first loading so see this is some html that i'm sure you're familiar with um i'm not familiar with any oh you're not okay i'm not familiar with someone but i do want to learn it okay well right here we have some html and it has a div id root and this root component is where we're embedding the um thing and yeah where are we loading the job logo can i change the logo logo yeah we could probably change it but like right now let's just leave it the same it's just a react one so yeah buddy um did you see that a man auntie amanda popped in no oh she did she comment hey what's up amanda okay yeah amanda welcome to the stream sister yeah what's up what's up we're writing some code we're doing react right now reaction writing some code okay export default app that's what i want export yeah x4 default game i know something after we're done with this um i'm gonna post um a comment on everything i um the that shows the cream game so you can play it and that so anyone can play it okay it's like it's like people on twitter can play it instagram can play it cool um youtube since we can post comments hey it's working [ __ ] up in her recommendations oh well that's good thank you for coming you you should hang out and watch i mean you don't you don't have to but um you could sista sista sista that's my sister my baby sister 16 years apart yeah the youngest she's the youngest of five i'm the oldest of five all right so we've got our the game appearing so let's add to this so i've got um inside of the game what i think we want to do is like i think we need to keep track of this the whole board and know so that we know like where the train is on the board and where the luggage is on the board um actually it um this always spawns here that always spawns there okay so let's try to let's just try to figure out how to render a bunch of squares onto the page so yeah so let's give this id board and then let's um let's iterate over squares squares actually um it's filler even a thing in it and unlike real code wishful was this thing in real code phil is yeah i mean sort of yeah are you i mean because we i really want to fill i'm like fill up the board of color hey can we first render a train all we need to do first is run your train okay so i think on the square like for each square we need to figure out like is the square a train square or is it a normal square so yeah so what we can do now is we can say like for all the squares which for now we can just say like um squares is a list of like one two three for all the squares we want to render a square which for now can just be like return um and a square can just be a div with the class of square oh i think in react this is different i think this is class name and then we can just say like x or something um but that's that's that's what we want for a square did i do this wrong oh yeah so i think if i just remove this actually just say square so we actually have functions in here oh yeah function called train called train yeah was that a function called train and then and then like and since since the since the tr the train is it has to be a whole function there are like a thousand things that need to be added onto the train okay what is that what does the train need like it like the train it like it needs co it needs a lot of code is lineup it needs like um some codes for the arrow keys that for what they're the keys to do okay okay um i also need some code for if touching is touching the wall good that's great yeah we'll die yeah um and i know something since you have to get you have to get the luggage and then luggage will appear in a different spot okay and then you go get that luggage okay then we'll go up here but you don't grow you you don't grow you don't grow okay so what i'm wondering is that like when we initialize the game um we're gonna get props right and then we have to say uh super props or something and then we say remember it's only us it's only us yeah why are we are we showing them any of it i mean like why are we showing them this oh you're right now i forgot yeah okay so we just added a constructor to the game we're adding a constructor here where chicken props we're calling super with props and then we're going to make a state and the game state is going to have squares and the squares i think i don't know should a square be hmm like like this isn't a square this isn't this is i don't know why are we just popping up squares so squares is going to be the tester i think we might want like a 2d array like i think we want an array where it's like um where we have a row where it's like x x x x x and then x x x x x and we just keep doing this until we have a board until we have a whole game board and then the position on the board so like zero comma zero talks about this square so what should that square be rendering is it populated with a train does it have a train does it have luggage does it have what we need in the middle the middle should be like the train right so if we would say like above that a boat so smack in the middle just like that huh yeah just snacking no okay and um all right so let's say we've got i think this is what kind of like what we want to do um but now the question is like do we want to store instances of the react component called square actually i know i know where so can you get a different letter for like right there like see so yeah this one is like luggage right so you say like that's an l so now the train has to like figure out how to like go down two and over two to get the l yeah and then you go this way see that no go that way now it'll go down that one is gonna be bad guy okay so let's say b for bad guy or v for villain okay all right so this is kind of what you're thinking right yeah that's like the whole game born for now like for now right there bye amanda bye amanda all right so i think what we want to do is i think we do want to have just components like if we have the react component directly in the square um yeah so let's make squares just like a giant list of react components we want i don't know yet but we'll see okay so um so how do we want to build this up we want to say something like um i think the game maybe the game should take in props where the props are like um height times width right so if we want to make a board that's like 20 by 20 then we'll get um there isn't any board it's just the whole screen i know i know but like you're not going to be able to tell there's a board but there is a board it's going to be like a secret board that you can't actually see there's a board yeah so like i think in appjs where we pass game right here we want to do like height is 20 and width is 20. something like that to start with right and so then here what we want to do is like is we want to iterate and make 20 rows t equals 20. yeah so um props dot height dot times do oh this is ruby this is not javascript width at times do this is ruby well we can't write ruby right here but i just want to like kind of show you what i think we want to do and then we want to add this uh we just want to say squares and then we add in oh that's a d your d or row is equal to a new thing yeah i know the d is the b doesn't work because this isn't ruby so this is kind of what we want to do but we want to do this in javascript so we want to say something like for r uh we know var we know four you know var and four uh-huh okay we know a ton of a kind of all but okay i'm going to call the variable r instead of i so that we know that it's rows so the outside one is rows and we want to say well r is less than props or like this dot props dot height this dot r plus plus i know i know what this dot does i want that there isn't squares is wrong there isn't squares there isn't square someone's born squares it's just a board that's all uh let squares equal this thing and then i'm thinking that we want like i don't know let's see so we want to create a new square or we want to create a new row let row equal squares equal that and then we want to say row dot append and we want to put pass in a new square where it's like what we need like squares i mean we're trying to okay so i created a class up here called square class square so a square is just going to be like a part of the board it's part of the grid on the board and right now each square is either going to have nothing or it'll have a train or it'll have luggage or it'll have a bad guy and so we need to figure out what we want to render on the square um we need yeah we can make it invisible we can make the square outline invisible so you can't really tell that it's how can you make him invisible well we'll have to play around with it i think yeah we'll just pull like zero which means the length let's make how fat it is zero okay and then we can make as close we want okay all right goofy but you can call you can pop into the background if you want to or you want to say something let our r has already been defined what do you mean where [Music] identifier has already been defined all right whatever i don't know why it's getting sad about that but unexpected token oh my gosh okay i see so this should be this and this should be this x is not defined oh yeah so then squares just becomes pairs um and then down here after we create the whole row of squares we want to say squares dot append row um new game row.append is not a function is it called push oh gosh i can't remember in javascript okay so now we want to say something like inspect and um okay so when there's let's see so i need to leave all those accents well right now they're uh yeah why isn't this showing up like you should not show up okay actually should not show up can you hear me um now it says stuff okay so i thought we'd be able to say something like this.props.x but not showing me anything so i think i got that wrong i like that i like that i know you like that because it's not showing anything uh like we need a new page so when you click to when you click the you click it and then it brings you to this new page where you play it there's a game that says there's a thing that says we start because when that says we start and you can only go up to and you can only win if you have you you win by getting 20 luggages okay but the luggage can't spawn where you spawn okay so what is going on like why isn't my um has anyone watched my season why doesn't why doesn't one of these props are why aren't these props available here by default do i need to like do something fancy um anyone anyone have any ideas with anyone hearing you then is anyone here they're looking if you look at the chat no one has closed anything so it looks like uh console so we got a ton of objects um dad how can we get um undefined um why okay so that should be creating an instance of square up right down right here what on the bottom oh oh here it is we don't actually want to pass anything we just want to render this. squares there we go cool cool cool those are all our squares they just don't look they don't look like they're in rows yet so maybe what we actually need is to also create like a row we need a new ornamental page to put the whole square stuff in right it's not gonna be on this page it's been on a different page like you're gonna you're just gonna click train game thingy oh well let's see if we can get it let's see if we can get it playing around float okay if this is play train game then they don't have to have no title there and it's just a sharp game it's not and it's not gonna have a title getting warmer it goes all the way to a high number so then yeah what if we just do like let's push the row and then let's push uh like vr yes we already have something like this unexpected everywhere so guess what he did to stop those hairs what he wrote down please encode on paper and then he was like and then he and then he tried it and it's like that doesn't that that part doesn't work in the code that's what that's what is starting like that's what starting i could learn in a long time is it yeah this wasn't in a long time that i've seen i've seen you use it okay so if s dot x no if s dot y is zero console.long s um when you do map let's see array map in javascript remember which argument will be the index and which one will be current value index and then the array we have the current value is the square we have the index which is i and then we have the array which is s which is s yeah child should have a unique key prop what is this key is number two string keys help react identify which items have changed are added or removed keys should be given to the elements inside the array to give the elements a stable identity so yeah but first i first of all we need to look at train emoji for me these and um when we search up train can i use your mouse and click the train i want and click the little train i want clicks a little what train i want click the little train you want there are more trains there are more emoji trains than just one or like there's more one smiley face there's more there's one there's one more there's there's more than one for everything oh oh oh emoji find out this like we're gonna put in the emoji what are we gonna put in the character is that um soon okay we just have to have we have to get the grid showing as a grid so what i was thinking of doing is while we're iterating over the squares if we're at the end of a row then we um then we do something so let's console.log s oh so s is all the squares and then the first one in the item dot props that's probably not how you're supposed to actually access it right um [Music] okay so we need to know console.log this dot props wow we're all right only using appjs looks like we're only using appjs right now okay so every time every time if i modulo this dot props dot height is zero then we want to console.log new line i think okay um you think that we're in the world has seen the word has seen the letter a who's i okay why is it only giving us okay so it is that is the row right so for each i see okay so for each oh s is not even okay squares is this is okay so this is a misnomer this isn't really squares this is like the grid so this dot squares dot map and then we want to say row because this is actually an entire row console.log row oh actually yeah so now we want to say like um return row.map row.map actually we just want to return a div class row with a row in it all right that was confusing for a second um and then here i think oh great somehow uh-oh okay did he drop off that's all right i guess crazy dropped off that's fine all right so then inspect we didn't drop him off he dropped off cool all right so then instead of making this uh the um there we go nice so this is too long upwards what do you mean it's too long it's too tall yes too tall okay so we go back to fps and we make the height smaller which makes the height of 14. there you go okay so then instead of the number though now we want to render um a state so the state we want here is how do we want to how do we want to make this state so a little bit faster i don't i don't want to waste time since i i like i would i want to get this done and i thought this is gonna be a quick a quick one since i'm gonna go a little bit quicker like like while you're coding i think we should also talk at the same time i'm trying like don't stop and then like okay so what is the position of the train the train spawns in the middle of the board every time runs in the middle of the board every time okay so then if we just say train is at um this dot props the height divided by two okay can we go yeah all right we're gonna just like pause here for a sec got it okay height times width um i think that should give us where the train is um then we need to figure out like um yeah we need to figure out how to make the train here so we have to find the square so if we make a method here called place train and it takes in a height and a width um or here yeah i just say x and y and then we can say let's find the squares we say this state dot squares [Music] we want to find a square so we say like return square dot x is equal to x and square dot y is equal to y yeah yeah so this is how you do a logical and between two like if you're trying to check two things are equal you use ampersand ampersand isn't that cool ampersand ampersand yeah that's this and sign and sign there it's called an ampersand can you even write that in time that i'm thinking that can you write that hand sign oh yeah on the paper [Music] okay then if we call like clair. square square dot set train i don't know does that work and then down here we can say like this dot state is equal to something and then like what if we say like uh um display is initially it's just empty but if we say uh set train then this dot set state for the display is equal to train emoji all right which one um that one okay and then down here i can just say like this dot state dot display oh and then we have to call it yeah so let's say [Music] i have to fill that down x is for y is five crashed can't cause okay yeah crashed so let's see why um um okay so this dot squares being a an array of arrays is kind of becoming painful so i'm thinking instead we just want to push onto squares and get rid of this concept of a row and just keep track of all the squares and where they're at and then down here this just becomes this dot state that squares what's the yarn lock no tiana um that's where we keep the dependencies for for yarn so it locks the dependencies at a specific version um so are you in yeah am i in yarn lock i was for a second but then i bailed out of it okay row is not defined where is row row's not even used refresh okay so if i scroll let's say display is just x if i modulo props this r is a thing for return i'm going to return a fragment with the square and then a br [Music] oh expected okay so i can't that's weird can i not do that square has already been has already been like that before that okay you duplicated what is going on here oh squares are already used i thought we set the key for it though we did objects are not valid as react child found object with keys square if you meant to render a collection of children use an array instead um so this should just be the thing oh uh okay all right so that's too wide yeah it's going to be five wide five tall my left is tall and five x is wide i know why can't i do this oh and then here nope why is this so hard react fragment can't use react fragment not uh oh okay let's just try the whole thing all right let's see here i expected oh all right so it was a different error okay so what is happening it could be four wide that was his float let's float it that was floating let's float it like like five x's wide five x is tall i thought we would be able to say like okay if it's not oh here we go let's see there we go getting warmer no it's not five x's wide because that's the tall it's more than five it's more than five wide cool um all right so this is play training place the train when we call place the train are we finding a square now find it playing the middle square that says five tall and five wide okay i don't think we're finding a square how do we how do people debug this stuff yeah so like in game right i want to put a break point right here and i want to refresh the page so that when wait is place train not even being called why not okay squares dot find square square dot x okay so let's see play and then we get in here square oh it's square.props.x square dot props dot x let's forget props that why we're probably not supposed to access those um i don't know okay cool so we found a square and it is at four five why is that why did i say look local host three thousand fair oh that's that's the port where we're running it so we're running it locally set square dot set train is not a function but it is it's right here set train set train square not set train square not set train we have to do something to make this like public is that it want to work all right what's happening when we get here square is an instance of a thing actually um all all the listeners um here so if you guys can i'm gonna make like something like this but not exactly like this like only you guys like um pick a different theme i picked a train themes um a train thing thingy and we had to put a different thing and make it work differently and then like i'll tell the people that they can make things like this so so i can look at other people who i've tried whoever have who have started to code on on some little stuff all right so this dot props dot on name change give me my new name all right so how do we push down context do we always need to like re-pass like how do i call set state on a child wait let's see the parent passes props and the child emits events so do we have to the props this dot props dot like i want to set the state on the child parent component toggle the menu okay toggle the child menu set this dot set state and then um okay so um does this square thing do we need to recreate these squares every single time from every time we render um like maybe x's right now um well i'm kind of wondering if this has to be inside of inside of here where we say like on squares and then here we say just this dot squares and then if um hey dude look look how much the camera's wiggling bud all right i think um are you getting tired do you want to bail on it um not bail but um oh they don't get down a little bit quicker okay but there's a lot so much there's a lot that goes into it i'm trying to go fast but there's a lot to figure out because i've never built this before i don't wanna i won't talk like as much as you're talking like not talking time just talk a little okay just talk very well little something code more than talk okay all right let's do it um let's see instead of calling place train let's see if we can do this a different way where we keep the trains position in state this uh train you delete the trigger and this will be like x is zero y is zero and here we say like if it's not state.trained.x do you know that boy do you know how to add this [Music] my finder i have what do you mean in my finder there's a picture of what the um to to get noise in my finder oh you have to break into my finder on my computer right on your computer we have to break into my finder that's on my computer okay you know how to do that um no i mean oh then that's really difficult i got it from and swim in the closing train you did yeah i paused it i took a photo of the thing but i only got one little thing it's we have to use garageband and record actually that remember how we got pikachu's recording um we should get we should try and get that in he's right try to get something like [Music] that i don't think we're going to actually finish this today i don't think we're going to be able to finish this today you don't think so yeah we're not going to finish this today if this dot props dot train and and we never play the train game i'm gonna change that play the train game let me change what says play the train game hey just play the train game yeah i'll change that to what um to a logo a logo okay yeah i thought you wanted to go fast well um it's just gonna be a quick look and then that's a quick logo why it's an emoji logo oh okay all right so let's just go to go to where that is when you have html then where is it let's just go fast what which logo do you want or which emoji uh i want to be sure to train okay and i want next next next next that one this one yeah okay happy that train it looks kind of like a trolley is it a trolley well i i don't care if i like it okay all right so then we have this game here then let's go quicker we're either displaying the train or we're displaying underscore uh just make it alright now we only need the arrow keys in the luggage we're gonna do the bad guy another time dad we're gonna do the bad guy another time okay um so what what's what's going on um let's just do luggage and skip the bad guy let's do that another time got it got it okay so if um right so we need luggage nice for luggage yeah okay so we want the luggage at like one one and that's the luggage is luggage at cr do the same thing okay let's say it is is luggage at cr and then we say luggage luggage okay and then up here can i tell you what the luggage looks like um sure let's go on to the [Music] luggage and then inside there luggage so if there's luggage the display should be luggage i was thinking like if we search a suitcase that literature but then which is like a suitcase and then like remember those like suitcase bags things that are like fun let me show you what i mean by [Music] [Music] okay so i think each square shouldn't it be like um let's say uh width like this like this right like this this one inside the luggage like this see this stuff see this piece of luggage like like where you have or you have the handle yes that part it cleans it like suitcase or something that one yeah okay what's it called briefcase that's a briefcase yeah but can't spawn the same place every time dad when you collect it when you go to that spot and collect it it should spawn in a different place oh and then you stay right there and go get it okay again and it adds to your score and then and then we'll be done for the day we're going to do the other stuff playing the bad guy another time so what are we doing what's next so um the arrow keys on that arrow keys so listen for arrow keys react um there's probably some library uh arrow keys react oh use key press react hook so i haven't used any react hooks before so let's try this hook out this hook makes it easy to detect when the user is pressing a specific key on their keyboard okay so that's all the stuff you have to do um oh wow it's just like wait yeah so this tells you okay so hmm [Music] state for keeping track of whether key is pressed so this is the hook use key press up handler set state use state false state for keeping track of whether the key is pressed if the key is pressed down and the target key is equal to the target key set key press true otherwise set key pressed false and then use the effect add event listeners so we pass this thing a callback and then an empty array ensures the effect is only run on mount and unmount return key pressed which is this thingy happy press sad press robot press fox press okay so let's try to add let's try to add a key press thing hook for our game right um actually let's add let's move let's move our square into square js too remember code more not talk more since you're talking more than coding that's code more than talking well the talking part is also useful for folks okay because i want i want to like talk through what i'm thinking so that i can try to figure out where i don't understand bits okay so we've got our game we've got our square we've got now we need to figure out what the key press thing is the situation with the key pressure since i think the keys will take uh how long do you think the keys will take i don't know a long time i think they'll take a long time you think so yeah oh okay so use key press so where is this happening it's in the app function but where would you register this if you were using class detection um you only register it there okay so where to use hooks react class component i'm tired already okay we're an hour in we're an hour in [Music] from classes two hooks introducing hooks hooks at a glance we're gonna have to um do some of this um a little later um uh i think i want to um not fail but um save it save some for later um not later but um save some for another day since i i don't think we're gonna finish it today today okay we're gonna save it for later all right well arrow keys react so can we save it for later uh if you want to bail you can go ahead um not velvet um you know don't you know what i want to do no i i i told you everything um that that that i want already so i i think we're not gonna do bad guys thingy i want to be able to move the train around let's let's get to the point where we can move the train around and we can get one point okay can we do that fast though no we cannot we cannot we have to go slow wow that's the only way we have to do it we have to actually do it right we have to write the code to do it can you make a harry potter castle with lego super fast no why it's because it has more pieces okay so this has more pieces too there's a lot of pieces that go into it right yeah okay um all right logy bud's going to go take a little break he is uh we're an hour into it in the afternoon it's tough for for young buck roos to hang in there for long long streams so we're just going to play around a little bit longer and then see how far we can get um i had a lot of learning to do here for react so still kind of just figuring it out and still very much in like the play around with games phase so i yeah i'm continuing to learn and uh um with the hopes that you know there's a lot of folks who really really enjoy working with react i think it's pretty good and we use it internally and um generally it seems fun to work with once you're like in an existing system um so i'm just trying to figure out like how you do some basic stuff in my in my down time here um yeah playing around with um how to get this all set up so okay so there's this error this arrow keys react component or thing that i installed and it just it just added 239 packages just to use arrow keys that doesn't seem right right like i feel like we should be able to figure out how to actually implement that by hand so let's let's try cleaning that up um so uh yeah okay so handle key down what do we how does this work handle key down to bind this the handle key down thing is a function that takes the cursor and the result if the key code is that and the cursor is greater than that then move the cursor around okay um yeah here's the react hooks flavored one a list item set hovered item use key press so this is like the same thing that i was just looking at but um use effect use effect okay so where is use key press actually used use key press arrow down arrow up [Music] all these are defined as functions is that like the new cool way to do this use effect is called and then you return this thing interesting i don't like is it is it that you use hooks or you use classes is that kind of like the difference um because it seems like a cool like a pretty cool way to do this but i just don't see folks doing that very much yeah i guess i'll have to do some research around around hooks versus class components here let's see does this one have a key key press no um okay listen to key press um in document here we go so when the component component did mount i think is when we want to add it right yeah okay so in in source in the game i think we want to say something like component did mount this is when it's in the dom like when the when the game is already rendered into the dom we want to then add a listener to the event target am i the event target though um handle key down document.addlistener so it's just adding it directly to the entire document okay interesting okay component did mount okay this dot handle key down right okay i think this is what sort of what we want um handle key down and we want to do something like this dot handle key down is equal to this dot handle key down dot oh actually yeah i can just bind it here so that we get back to ourselves okay so then i say handle key down and this should take an event console.log e and then when i come over here and i refresh the page if i go to the console um cool and if i say left right up down so eat up prevent default so don't scroll and then we want to say like if e dot key is equal to arrow up then we want to do something um actually yeah switch on e dot key javascript switch statements case arrow up we have to break after each yeah down um left right uh so what seems to be happening is that now like the more that i use it the more that i'm like okay so now there's one two three four five six different event listeners um so we gotta fix that for sure um because we only want it to fire once so document.add event listener component bid mount like i thought this was the only time that it would mount but is what's going on here expect the default case okay face arrow left if i refresh the page hard refresh and then we say left right left right up down up down up down down down down down down up up up up down left right off straight that seems like it's actually doing what we want so um i think instead of like i think what we want to do is if we're going up we want to set the state so the train moves up if we're going left we want to set the state so the train moves down um so move train up and this is going to be like this dot set state train is equal to this dot state dot train at x plus one why is this not stayed down not y maybe i can do um this dot state dot train and then x is this dot state dot train dot x plus one see well okay that doesn't actually work because we're already in the top row maybe or no we want it to actually go down right uh oh we're not calling it okay i think that may have worked um let's in here let's console.log state this dot state train is now at -1 okay so we should say like only go if this.state.train.x is zero then return or this dot state dot train x is um equal to this dot props dot height oh no because yeah um oh okay so we shouldn't if we're going up we should never worry about the bottom so this should be fine this should be sufficient um and then move train down should be basically the same thing um except where we want to check the the height and we want to add to it so that it moves down and instead of this we want to say this dot props dot height if i let's not move the train down i use the down arrow um okay train.x move train down so when i hit the down arrow oh interesting so it's moving but it's moving the wrong way um yeah because we want to change why don't we we want to change y so this should be y um this should be y this should be y i always mix up my x's and y's and i'm sure they're probably broken or wrong or something but whatever hey okay so now it's moving it down [Music] um okay so up is not working anymore uh why okay so now we can move up and down the ladder sort of at least we're like landing in a weird spot but that's okay same thing for left and right there's probably a better way to do this right okay so move left if we're subtracting by one and that equals zero or if that equals a negative one then we don't want to go there if we are increasing and x plus 1 is equal to the width then we don't want to go there y plus 1 is height then we don't want to go there um all right so let's see if i can move around i forgot to call it so let's call it down here so we're going to say this dot move train right and move train see what happens here all right refresh uh hard refresh and then okay that's cool uh i fell off though um x is 26. see 21. did i appear back onto the okay i'm back all right so now the states cool um so now we want to try to like get the luggage so we want to try to find the same exact well okay let's make it so that the doesn't look as bad so we can add a square.css and then here we can say import right i think that's how we do css yeah okay so then we just have like a square component right rs dot square and we can say height is 10 pixels width is 10 pixels border 1 px solid oh did something crash nope um source all right so we're firing back up here all right each child in a list should have a unique key prop check the render of game game method so did these not have a key prop i thought they did oh span class square is that what it's um uh where are we creating squares that's a key property right here is that not what it wants um am i not using it like i saw i thought this should contain oh wow the key is not even in there interesting why isn't that yeah this key prop right here should be i thought should be rendering right only do this if items have no stable ids there's no need to specify the key here why not wrong the key should have been specified here okay which is what i did right um number two string yeah okay and then the list keys must only be unique among siblings right like um i don't understand how this is not doing that like maybe someone else knows and can leave a comment below um but yeah i thought that this was creating the key property with column dash row but with weird as i don't see that coming out as a prop down here oh key is undefined what's up with that huh why what if i do like c times r plus no let's see c plus one times r plus one no that's not i don't think that's unique either [Music] um render what okay so here's my other thought is that i'm rendering these like every single time we call render i'm creating a whole bunch of new squares like a whole set of new squares and re-rendering all of those i think because squares is not part of state because i don't think there's a way to set down or like to pass down the state right like so this should be yeah i think that should work fine but i'm still getting this error header div what is up with that in the render method of game we're in game and we're in the render method and i don't think no i don't think this is working so um all right well whatever so let's see inspect um each of these have a class of square square square square square square and then a br so over here okay um 50 pixels uh huh what is going on here is this not um there we go display inline block okay so the place where the brs are something's incorrect here when we first render the page the train is at zero zero right and then if i hit right right okay so i should not be able to hit right again because that would push me off the end and i did um so something is wrong with my uh with my math around like whether or not it's allowed to go left or right um okay so we've got how many let's let's change the game so it's much smaller so that we can see here let's just do like five by four so we know there's there's a difference so five high wait okay so this is wrong i have my height and width mixed up so height and width we want these to be opposite okay wait no all right we're still rendering [Music] four high which means this br should be after the width modulo is zero okay okay so i don't think we should be able to like hit right right right and then if i hit right again it should do nothing but instead it's going down to the next um the next square so i think there's a couple things that are borked in terms of like x and y um okay height height is y height is up and down height is up and down height is y right yes so always make x and just x right x is our width y is our height why why x x x y okay and oh that's fun um okay so with the width right we set the width to four i believe we did so the width is four so zero one um when we move the train up and down that should be moving on y and it is and up and down is based on height and it is so when i hit the right arrow move train right um if the street okay so if the state's x plus one so zero one two 3. so if 3 plus 1 is 4 and 4 equals this thing then just return that's what it should do but when i hit right so then on render that's uh console.log state dot train dot um x okay so if i hit right one two three four should do nothing it should not going up okay so something is up in our game so move train right if x is equal to this dot props that width minus one let's see if there's something to do with like there we go i have a hunch the hunch is that by doing it this way we are converting width into an integer like i think width might be a string or something um all right now our our problem is different right now our problem is that up and down also don't work so um all right so up when we move the train up when i hit the up arrow we want the trains position to move down so let's see console.log x or this is y now so okay so the numbers are correct and then there's at the right boundaries but it's updating the wrong thing i think what in the world okay so where is my is this at is x at or is y at is train at x is the width y is the height so is the train at that position x y x y um okay so uh let's put yeah let's put in the square like for display of the square let's put its x and y just so we can see that um this dot props dot x and y zero zero zero one wait why is zero there y is y zero okay so when our squares are being initialized they're being initialized incorrectly i think this is correct this is correct this is correct this is correct okay left and right is working left and right is working [Music] and up and down is working okay that was too hard all right so then if we get the luggage then you get a point or something but um i think this is working now okay and all right whatever so um yeah since logan has sort of lost interest i think we'll call it there since it was kind of just going to be like a fun little thing that we were playing with together so uh yeah hopefully that was useful i don't know i learned a couple things um about like ways that i might approach this uh and i think it'd be super fun to build a a snake game eventually but for now um yeah i think i'm just going to call it there yeah it's all right okay see you later

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