Pygame Platformer Part 4: Jumping

Key Takeaways

welcome back this is part four of our platformer game project and we finally gotten to the one you've all been waiting for uh we're going to make our character jump so we have our game uh right now where we have our Sprite with gravity that acts on it that can run back and forth and we can stand on platforms that's good but now we want to talk about jumping so what I've done um since the last time um I did go ahead and I went over here and I added uh a variable here for player gravity in our settings so that in our player Sprite we can just use that here instead of putting the number um that way those of you who want to adjust gravity make your make the gravity in your game different bigger or smaller um you can just change that value right here okay so so how are we going to do jumping well at this point is when I always get lots of questions about uh things like double jumping and um and wall jumping and all that kind of stuff but and we we'll get to that but uh for right now I just want to talk about the very simple jumping where you press a key and you jump in this case the space bar now we don't really want to do it the way we did the keys because we don't want to jump as long as we're holding it down right that would be flying not jumping right if we had pressing the space bar accelerated Us in the negative y direction that would would be like a a jetpack game or a or it' be a good way to do a lunar lander kind of game where you launch your rocket and you thrust upwards and then um when you're coming down you want to thrust again to to slow down and and and land gently uh but that's flying not jumping so what we want to do is we want to go over to our game uh event section and add a an event for the key press uh for the key down so we want to look for the pg. key down event and the and the key that we want to look for is pg. kpace and if that happens we're going to say player. uh jump all right now what do we need to do in player. Jump well over here in our player when we Define jump there a couple things we could do well we could just say we could just say JUMP means self. v.y equals uh -20 or something like that right and that gives us an upward speed and that's fine that will make us go upwards but the problem is that it's going to do it whenever we hit space so if I go over here and Run the game you can see um whenever I hit space I jump right so I can keep hitting it and go higher um which is fine if you're making Flappy Bird or something um um where flapping makes you go up gravity makes you go down uh this is not much of a platform game because we never we could just run around and Never Land on anything okay so here's what we want so what we want to do is we only want to be able to jump if we're standing on something right and how do we tell we're standing on something well we're standing on something if there's something below us so if we just look one pixel below where our Sprite is see if we if there's a platform there meaning see if we collide with a platform then we know we're standing on something and we're allowed to jump so that means in here we need to check to see if we're standing on something right I'm going to go ahead and put that here jump only if standing on a platform okay so we need to be able to check the platforms but the player Sprite doesn't know anything about the platforms player doesn't know they exist so what we can do is over in our game Loop when we spawn the player we can basically send the player it's called a reference we send it a link to the game and then it knows all about all the games variables including this platforms group right so when our player spawns it knows about the game and we can say self. game equals game and now the player has a essentially a copy of the game it's not really a copy it's a reference but um it knows about everything that's part of the game and that means that we can go right here and do that Collision so we want to look underneath us so we want to take the rectangle of the of the player Right add one to it so one one pixel lower we do our Collision just like we've done before for right we Collide our self with the self. game. platforms still false and then we don't really want to be inside the inside the platform so we move the rect right back up again and so this happens right away so it's you're never going to actually see this because there's no drawing or updating happening between these two commands so all we're doing is just shifting it down temporarily to see if there's anything below us if there is then we can jump okay so let's see how that looks let's go over here run our game and there we go okay so that's much better so you can see if I'm if I hit space again while I'm in the air nothing happens right until I land back on the platform then I can jump again right very cool can jump around it's already lots of fun I can jump around ah except now we see something strange right when I jump so I'm snapping to the top of this platform right if you think about how we did the platform collisions for falling um it'll be kind of obvious why it's doing that right we start jumping up and then as soon as we touch a platform we're instantly snapping to the top of it and setting our velocity to zero so that's not good right we don't want that to happen and for this game since I'm thinking about doing this as sort of a if you're famili with Doodle Jump kind of game um I do want to be able to jump up through the platforms I just don't want to snap to them like this so I want to be able to jump up and then land on it so I actually only want to land on things when I am going downwards not anytime so in our update right here we're just checking all the time to see if we hit a platform all right this is the part I should have labeled this last time uh check if player hits uh hits a platform only if falling right so only if falling so how do we tell we're falling well it means our velocity is downwards or greater than zero so if player do X the x of the player or sorry the Y of the player not the x is greater than zero okay then we can do all of this stuff but not if it's not okay so that's going to look more like this okay so I still jump like I did but if I'm underneath it I jump up and land on it okay so that's much more doodle jumpy and works the way we want it to for the game that we're going to be making now obviously there are lots of other ways we could do this um sometimes in game you don't want to uh jump to the top of it right or be able to jump through it you would want jumping up like this to stop you when you're head hit the platform um and if you come in from the side right now we have a thing where if we come in from the side we're going to land on the top um because we're only really looking at the top um now that's fine for this game um to do collisions in all four directions to a platform is a little more complicated in the code so I'm going to hold off before we add that until we've explored a little bit more of how to get this simple Doodle Jump Style game working then we can talk a little bit more about how um how we're going to make something more advanced work okay so try that out um you can go ahead and add some more platforms if you want although I think we have I'll take a few more minutes to to talk about a simpler way to add more platforms without adding them uh one at a time like we're doing uh like we're doing here so what I want to do is just set up a list of the platforms that I want uh on the screen when it starts kind of like the the start screen okay and I'm going to go over here and I'm going to add that to our settings platform or we'll call this starting platforms because we're going to do other things with the platforms later okay so let's just call it the platform list okay and this is just going to be a list of a bunch of platform coordinates right now I know the first two that I want to do I want to do this one right because I want to make the the one that's on the ground okay and then I'm going to do a comma and I'm going to do I'll just go ahead and do this second one right that's a good one to do and then we could add a few more now you can play around there's different ways you could do where you want to put them just remember it's it's the first number is the X right so the second number is the Y so like you could do something like height minus 350 and that would be 350 pixels from the bottom um the width of the platform and the and the thickness of the platform okay and I'll do a couple more just so I have a good assortment of uh platform on the screen you can play around with these numbers uh put them in different places um you know obviously if you wanted a smaller platform I'm doing them all at 100 we could do this one could be a nice skinny one right but then I have a list of one two three four five platforms that are going to show up on the screen uh at the start of the game okay so once I have that list that's just a list of you know sets of four numbers that I'm going to use to create each platform so over here instead of all of this we're going to do a loop and just Loop through we're going to Loop through this list and use the first entry in the list is this set of four second one third one right and it'll just make each one so I'm going to sa for just call it a plat for short that's another little abbreviation I like to use for Platforms in uh platform list okay so for each one of those I want to make a platform so let's just call it P platform right and then we know we have to put the four numbers now now there's two ways we can do this we could say uh plat zero right plat one plat two and plat three right and that would do the the zero the one the two and the three item in the list but there's a shortcut for that if you want to take a list and break it up into all of its pieces just like we're doing here that's also called exploding the list so in Python we just say star plat right the star stands for explode in this case so take the plat take that list and explode it into its four components and then we have a platform and we just add the platform the platform to the all Sprites list and to the platforms list right and that's a lot less uh that's a lot less verbose than doing it all one at a time and if you want to change them you can go over and change those coordinates let's see what that looks like all right there we go now I've got some different platforms that I can jump to um and bounce around the screen and you can play around with that you can do fun stuff like jumping off the side and landing on another one that's going to be a good strategy maybe um okay and so we'll stop there for now uh play around with how it works try changing some of those settings right that's why we that's why we put them in the settings uh file here and what I recommend you do though is just make sure you have for moving forward make sure you have not too many platforms but not too few um and a good spread of them so that you can get up to the top of the screen because next video we'll start talking about how are we going to scroll this scroll the screen when we get up near the top or move the camera if you like to look at it that way how are we going to keep going higher and get to more platforms all right thanks I'll see you next time