Style Guide

https://leanpub.com/playdatebook

Lua Styles

https://leanpub.com/playdatebook

Project Structure

https://leanpub.com/playdatebook",{"_508":509,"_43":44,"_47":48,"_45":46,"_65":66,"_510":511,"_646":506},"previewContent","

\nIntroduction\n
- \nFeedback\n
- \nWhat to Expect\n
- \nGetting the Most Out of the Book\n
- \nGetting Started\n
- \nNext Steps\n
\n
\nHello, Playdate!\n
- \nCounting Frames\n
- \nMoving the Text\n
- \nPlayer Input to Change Greeting\n
- \nA Gentle Introduction\n
\n
\nTennis\n
- \nDisplaying the Paddle\n
- \nMoving the Paddle\n
- \nDisplaying the Ball\n
- \nRefactoring playdate.graphics\n
- \nMoving the Ball\n
- \nBounce Off the Wall\n
- \nBounce Off the Paddle\n
- \nRefactor into Functions\n
- \nAngles\n
- \nSpeeding Up the Ball\n
- \nScore\n
- \nSound Effects\n
- \nFinal Code\n
- \nExtra Credits\n
- \nWhat’s Next\n
\n
\nClock\n
- \nDrawing the Time\n
- \nRespecting Preferences\n
- \nPadding Zeroes\n
- \nLowering the Framerate\n
- \nShowing Power Details\n
- \nCustom Font\n
- \nFinished Source Code\n
- \nExtra Credits\n
- \nWhat’s Next\n
\n
\nSnake\n
- \nMoving on the Grid\n
- \nControl the Snake\n
- \nSpawning Apples\n
- \nAdding Snake Pieces\n
- \nDon’t Spawn an Apple on the Snake\n
- \nGame Over\n
- \nRestart the Game\n
- \nHigh-Score\n
- \nReset High-Score\n
- \nFinished Source Code\n
- \nExtra Credits\n
- \nWhat’s Next\n
\n
\nSoaring\n
- \nControlling the Bird\n
- \nSpawning Trees\n
- \nCrank Indicator\n
- \nScenes\n
- \nRefactoring Gameplay Reset\n
- \nIntroducing a State Table\n
- \nBreaking Our Code Into Multiple Files\n
- \nExtra Credits\n
- \nWhat’s Next\n
\n
\nSokoban\n
- \nMoveable Player\n
- \nPushing a Box\n
- \nTarget Spot\n
- \nCounting Steps\n
- \nPreparing for Complexity\n
- \nMultiple Boxes\n
- \nParsing Levels\n
- \nLevel Select\n
- \nExtra Credits\n
- \nWhat’s Next\n
\n
\nDungeon Crawler - Part 1\n
- \nDrawing Player from a Tilemap\n
- \nDesigning Levels with Tiled and Rendering Them\n
- \nPlayer Movement with Camera\n
- \nMap Collision Detection\n
- \nTalking to NPCs\n
- \nExtra Credits\n
- \nWhat’s Next\n
\n
\nDungeon Crawler - Part 2\n
- \nOrganizing Our Code\n
- \nMultiple Maps with Stairs\n
- \nRandom Encounters\n
- \nCombat\n
- \nPlayer Stats & Enemy Attacks Back\n
- \nDeath\n
- \nExtra Credits\n
- \nWhat’s Next\n
\n
\nPlaydate by Example\n
- \nText\n
- \nAudio\n
- \nDebugging\n
- \nCapturing Gameplay Footage\n
- \nRelease Steps\n
\n
\nOutro\n
- \nStart Small\n
- \nReleasing Your Playdate Games\n
- \nContinue to Learn\n
- \nBacking Up Your Games\n
- \nBeyond Playdate\n
- \nGame Development Tools\n
- \nAssets\n
- \nThanks & Credit\n
\n
\nPlaydate Cheatsheet\n
- \nSystem\n
- \nDisplay\n
- \nDraw Text\n
- \nImport Files\n
- \nInput Handling\n
- \nSprites\n
- \nGraphics\n
- \nImages\n
- \nTimers\n
- \nSound\n
- \nSave Data\n
- \nAnimation\n
- \nSystem Menu\n
- \nLifecycle Callbacks\n
- \nCoroutines in playdate.update()\n
- \nCommon Patterns\n
- \nQuick Constants Reference\n
\n
\nLua Cheatsheet\n
- \nVariables\n
- \nFunctions\n
- \nTables\n
- \nStrings\n
- \nControl Flow\n
- \nOperators\n
- \nCommon Patterns\n
- \nUseful Built-in Functions\n
- \nCoroutines\n
\n
\nStyle Guide\n
- \nLua Styles\n
- \nProject Structure\n
\n

Introduction

Make Games for Playdate with Lua is a comprehensive guide to creating simple games for the Playdate handheld video game console. This book is perfect for beginners. You’ll code, from scratch, a bunch of small games to learn the fundamentals. We’ll use the Lua programming language to write our code. If you’ve written some code before, you’ll catch on to Lua quickly! If you haven’t coded before, don’t worry at all. Lua is great for beginners because of its simplicity and similarity to the English language.

Playdate’s simplicity and constraints make it a great learning platform. We’ll embrace its limitations in resolution, color, and input to focus on learning how to make fun games. It’s truly special to be able to write code and be able to play it on an actual handheld game console within seconds. Playdate’s approachability and developer friendliness are unrivaled in the game development space.

Together we’ll code games from scratch, learning key concepts and increasing the complexity with each chapter.

Feedback

If you run into any issues or have any feedback, send me an email at brett@brettchalupa.com.

What to Expect

We’ll start by displaying some simple text on the screen. Then we’ll code our first game—a minimal version of tennis inspired by Pong. From there we’ll continue to code different games and utilities together. I’ve got lots of ideas for what to cover, like the classic Snake to a minimal Vampire Survivors clone to a fishing game with the crank.

Each chapter will contain a complete project with the code from start to finish explained.

The source code for each chapter can be viewed and downloaded on GitHub at https://github.com/brettchalupa/playdatebook.

Files on your operating system are referenced using the / to represent the folder. If you see reference to a file in this format: source/player.lua, it means within the folder named source there should be a file named player.lua. Linux and macOS use / but Windows uses \\ to delineate folder paths, but for the sake of simplicity, the book uses / throughout.

In some of the code examples, there will be -- snip if there’s code that was removed from the example but would otherwise be in your file. It helps focus the example code and remove the clutter around what’s being explained.

1 -- snip\n2 \n3 playdate.graphics.drawText(\"Hello, Playdate\", 40, 40)\n

\n\n

Don’t actually type in -- snip. It’s just to show you there was code from a previous point in the chapter that is unchanged and excluded for brevity.

Getting the Most Out of the Book

The best way to get better at programming is by writing code. The more code you write, the easier it will be to implement your ideas. It takes time to get used to thinking in code, learning the language, and understanding Playdate’s SDK.

I encourage you to do four things as you go through the book:

\nType out the code yourself. Don’t copy and paste it. You’ll learn the language better by typing it yourself, and it’ll become muscle memory.\n
\nExperiment! It’s okay to change the code and deviate from what’s in the chapter. Make what you’re coding your own.\n
\nBack up your code. Make copies of your code before you modify it so you have backups. When things are working well, consider zipping it up or duplicating it. Sometimes when coding you can dig yourself into a hole that’s difficult to get out of. While this book will not cover version control, if you’ve heard of Git before, it helps solve this problem by making it easy to back up and track changes to code.\n
\nSearch online to learn more. No book can contain answers to everything. An important aspect of coding games is learning how to learn—being able to search for and apply solutions to problems you’re running into. There are imperfections and room for improvement in each chapter, with suggestions for how to take the projects a step further on your own.\n

Getting Started

The first step is to download the Playdate SDK from the Playdate website. The Playdate SDK contains everything you need to make games for Playdate—example code, a simulator to run your games, a compiler to build your games, a manual called Inside Playdate with design guidelines, and more. The Playdate SDK supports Windows, macOS, and Linux.

The Playdate SDK is quite stable, so what’s covered in this book should (hopefully) work with newer versions. This book was written and tested against the 3.0 Playdate SDK.

Installing the SDK

How you install the SDK depends on your operating system:

macOS: Open the .pkg file you downloaded and follow the installer. It’ll install the SDK, the Playdate Simulator, and a command line tool called pdc (the Playdate Compiler) that we’ll use throughout the book to build our games. The installer takes care of everything for you.

Windows: Extract the downloaded .zip and run the Setup.exe installer inside it. This installs the SDK, the Simulator, and pdc.

Linux: Extract the downloaded .tar.gz, move the SDK folder to wherever you’d like to keep it (your home directory works fine), and then run the setup script inside it:

1 sudo ./setup.sh\n

\n\n

This installs pdc and the Simulator.

Setting Up the Environment Variable

When you install the SDK, the installer sets an environment variable called PLAYDATE_SDK_PATH that points to where the SDK lives on your computer. An environment variable is just a named value that programs on your computer can look up—think of it like a global setting. pdc and other tools use PLAYDATE_SDK_PATH to find the SDK’s files, and we’ll use it later to set up autocomplete in our code editor.

The macOS and Windows installers set this up for you automatically. On Linux, you’ll need to add it yourself. Open your shell configuration file (~/.bashrc for Bash or ~/.zshrc for Zsh) in a text editor and add this line, replacing the path with wherever you put the SDK:

1 export PLAYDATE_SDK_PATH=/home/yourname/PlaydateSDK\n

\n\n

Save the file and restart your terminal for it to take effect. You can verify it’s set by running:

1 echo $PLAYDATE_SDK_PATH\n

\n\n

If it prints the path to your SDK, you’re all set.

The installer also adds the SDK’s bin folder to your system PATH, which is what lets you run pdc from any folder in your terminal. If you ever run pdc and get a “command not found” error, it means the SDK’s bin folder isn’t on your PATH. You can fix this by adding the following line to the same shell config file:

1 export PATH=$PATH:$PLAYDATE_SDK_PATH/bin\n

\n\n

Your Code Editor

The only other thing you need to make games for Playdate is a text editor for writing code. Your text editor is different than Microsoft Word or Google Docs. It’s a plain text editor that’s specifically just for entering characters—your game’s code.

If you don’t already have a code editor, download Visual Studio Code. It’s free, available on Windows, macOS, and Linux.

\"Screenshot — Figure 1. Screenshot of Visual Studio Code

Some other popular code editors are Zed, Sublime Text, Notepad++, and Nova (made by Panic for macOS, the creators of Playdate).

Setting Up Visual Studio Code for Playdate

If you’re using Visual Studio Code, there’s a bit of one-time setup that’ll make coding games for Playdate easier. It’s easy to set up and gives you autocomplete for Playdate’s SDK functions—so when you start typing playdate.up it’ll suggest playdate.update() and so on. It’s not required, but it’s nice to have.

First, install the Lua extension by sumneko (also called LuaLS). Open Visual Studio Code, click the Extensions icon in the left sidebar (or press / ), search for “Lua”, and install the one by sumneko. This gives you syntax highlighting, error checking, and autocomplete for Lua.

Next, you need to tell the Lua extension where the Playdate SDK lives so it knows about all the Playdate functions. In your project folder, create a .vscode folder and a settings.json file inside it:

1 .vscode/\n2   settings.json\n

\n\n

Add the following to .vscode/settings.json:

1 {\n2   \"Lua.workspace.library\": [\"${env:PLAYDATE_SDK_PATH}/CoreLibs\"],\n3   \"Lua.runtime.nonstandardSymbol\": [\"+=\", \"-=\", \"*=\", \"/=\"]\n4 }\n

\n\n

The first setting points the Lua extension to the Playdate SDK’s core libraries so it can provide autocomplete and documentation for Playdate functions. The second setting tells the extension that Playdate’s Lua supports shorthand operators like += and -=, which standard Lua doesn’t have. Without it, you’ll see false error squiggles in your code.

This uses the PLAYDATE_SDK_PATH environment variable we set up earlier. If for some reason autocomplete isn’t working, make sure that variable is set correctly. You can also replace ${env:PLAYDATE_SDK_PATH} with the actual path to your SDK, like \"/Users/yourname/Developer/PlaydateSDK\" on macOS or \"C:/Users/yourname/Documents/PlaydateSDK\" on Windows.

You’ll want to add a .vscode/settings.json to each new Playdate project you create. It’s a small step, but it makes a big difference when you’re writing code.

Next Steps

If you decide to use the Zed editor, you can follow these steps to set up Lua and the Playdate SDK with autocomplete.

Because the Playdate SDK includes the Playdate Simulator, you don’t actually need the game console to make games for it. You’ll be able to test drive the SDK and experiment without spending any money. But I’d recommend buying a Playdate as you’ll want to test your game on it and play others’ games. The processor of the Playdate is much slower than your computer’s. That means if you write slow code, it may run fine on the simulator but be unplayable on the actual Playdate. You’ll want to test early and test often on your device if you’ve got one.

Once you’ve got the Playdate SDK installed, your environment variable set, and a text editor ready to go, you’re all set to start making a Playdate game!

-# Part 1: The Basics

Hello, Playdate!

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Counting Frames

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Moving the Text

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Player Input to Change Greeting

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

A Gentle Introduction

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Tennis

Let’s code a simple game of single player tennis inspired by the classic Pong. We’ll code a paddle that we can move up and down the screen with the d-pad or crank. When the ball hits the top, right, and bottom of the screen, it’ll bounce off it. If it goes past our paddle and off the left side of the screen, it’ll be game over. We’ll keep track of how many hits we get. And to add a little difficulty to our game, we’ll make the ball get a little bit faster over time.

Displaying the Paddle

Start off by creating a new folder called tennis with a source folder that contains source/main.lua.

Put the following into source/main.lua:

1 function playdate.update()\n2   playdate.graphics.fillRect(36, 80, 12, 48)\n3 end\n

\n\n

playdate.graphics.fillRect draws a rectangle on the screen and fill it black (the default fill color). The first parameter is the x position, the second is the y position, the third is the width, and the fourth is the height. Our code says to draw a rectangle at 36 pixels in, 80 pixels down, with a width of 12 pixels and a height of 48 pixels.

\"Filled — Figure 2. Filled rectangle displayed on the Playdate Simulator

Let’s make it so we can move the paddle. This won’t be too different from moving text around the screen. But this time let’s use a table to keep track of the paddle position and use key-value pairs to make our data structure more clear.

Lua is quite flexible in that it allows key-less tables, like we saw with the different names, local names = { \"Playdate\", \"Goku\", \"Bulma\", \"Piccolo\" }. But Lua also allows us to specify keys and values for easily accessing and changing them. We’ll see this in action, but here’s an example of the alternative way of using a table:

1 local player = {\n2   name = \"Oolong\",\n3   health = 10,\n4   level = 5\n5 }\n

\n\n

The values of player can be accessed with dot syntax (player.name which returns the string \"Oolong\") or with bracket syntax (player[\"health\"] which returns the number 10).

Let’s update source/main.lua to introduce a paddle table that has an x and y position:

1 local paddle = {\n2   x = 36,\n3   y = 80,\n4 }\n5 \n6 function playdate.update()\n7   playdate.graphics.fillRect(paddle.x, paddle.y, 12, 48)\n8 end\n

\n\n

We’ve refactored our code to keep track of the paddle’s position in a table named paddle. Very convenient.

Bonus: put the paddle’s width and height into the paddle variable and reference it from the variable when drawing the paddle.

Moving the Paddle

Let’s move the paddle. We’ll start with the d-pad and then support the crank. Much like with moving the text, we’ll check for the up and down input on the d-pad.

Update source/main.lua to be:

 1 local paddle = {\n 2   x = 36,\n 3   y = 80,\n 4     s = 10\n 5 }\n 6 \n 7 function playdate.update()\n 8   if playdate.buttonIsPressed(playdate.kButtonUp) then\n 9     paddle.y -= paddle.s\n10   end\n11 \n12   if playdate.buttonIsPressed(playdate.kButtonDown) then\n13     paddle.y += paddle.s\n14   end\n15 \n16   playdate.graphics.clear()\n17   playdate.graphics.fillRect(paddle.x, paddle.y, 12, 48)\n18 end\n

\n\n

Our expanded code moves the paddle up and down by paddle.s—a new entry in our table that represents the paddle’s speed. By having it live in just one place, it’s easy to change the value to find a speed that feels right. Try changing s around to find a speed that feels good to you.

We also had to make sure we clear the screen every update with playdate.graphics.clear().

Did you notice that the paddle can be moved off the screen? Penalty! Out of bounds! Well, no, not really. But a bad player experience. Let’s make it so that the paddle can’t go outside the bounds of the screen of the Playdate.

We’ll introduce a condition within our checks for buttons being pressed. For up input, we’ll check to see if the paddle’s y position is less than or equal to 0, and if it is, then we’ll set it to 0. For down input, we’ll check to see if the height of the paddle plus its y position is greater than or equal to 240, which is how many pixels tall the Playdate is.

Let’s code that up in source/main.lua:

 1 local paddle = {\n 2   x = 36,\n 3   y = 80,\n 4   s = 10,\n 5   w = 12,\n 6   h = 48,\n 7 }\n 8 \n 9 function playdate.update()\n10   if playdate.buttonIsPressed(playdate.kButtonUp) then\n11     paddle.y -= paddle.s\n12   end\n13 \n14   if playdate.buttonIsPressed(playdate.kButtonDown) then\n15     paddle.y += paddle.s\n16   end\n17 \n18   if paddle.y <= 0 then\n19     paddle.y = 0\n20   end\n21 \n22   if paddle.y + paddle.h >= 240 then\n23     paddle.y = 240 - paddle.h\n24   end\n25   playdate.graphics.clear()\n26   playdate.graphics.fillRect(paddle.x, paddle.y, paddle.w, paddle.h)\n27 end\n

\n\n

Now our paddle stops at the top and bottom of the screen. We have to check that the paddle’s y position plus its height is less than the screen height because paddle.y is the top of the rectangle. And the x position is the left side.

There’s an aspect of this code that I don’t love, and it’s 240. When coding, a number that’s present without any context to its meaning is known as a magic number. It’s difficult to know what 240 means at first glance. While we know it’s the height of the Playdate’s screen, it’s not obvious. Our goal is to write code that’s easy to understand. We could make a variable, local screen_height = 240 and reference that. But we’ve got another option that’s a little more futureproof. Playdate provides an API to get the height of the display: playdate.display.getHeight()

 1 -- snip\n 2 local displayHeight = playdate.display.getHeight()\n 3 \n 4 function playdate.update()\n 5 \n 6   if playdate.buttonIsPressed(playdate.kButtonUp) then\n 7     paddle.y -= paddle.s\n 8   end\n 9 \n10   if playdate.buttonIsPressed(playdate.kButtonDown) then\n11     paddle.y += paddle.s\n12   end\n13 \n14     if paddle.y <= 0 then\n15         paddle.y = 0\n16     end\n17 \n18     if paddle.y + paddle.h >= displayHeight then\n19         paddle.y = displayHeight - paddle.h\n20     end\n21 \n22   playdate.graphics.clear()\n23   playdate.graphics.fillRect(paddle.x, paddle.y, paddle.w, paddle.h)\n24 end\n

\n\n

This introduces a variable displayHeight that’s set dynamically from the Playdate SDK and removes the magic number.

Let’s whip the crank out and have turning it move the paddle up and down. Cranking forward will move the paddle down, while cranking backwards will move up. The Playdate SDK provides the playdate.getCrankChange() function, which returns two values: the degrees of angle change since the last time the function was called and an accelerated change value based on how fast the player is moving the crank. We’ll use the second value, the accelerated change, since it feels better.

Add the code to source/main.lua between the d-pad input checking and the boundary checking:

 1 -- snip\n 2 if playdate.buttonIsPressed(playdate.kButtonUp) then\n 3     paddle.y -= paddle.s\n 4 end\n 5 \n 6 if playdate.buttonIsPressed(playdate.kButtonDown) then\n 7     paddle.y += paddle.s\n 8 end\n 9 \n10 local _crankChange, acceleratedCrankChange = playdate.getCrankChange()\n11 paddle.y += acceleratedCrankChange\n12 \n13 if paddle.y <= 0 then\n14     paddle.y = 0\n15 end\n16 \n17 if paddle.y + paddle.h >= displayHeight then\n18     paddle.y = displayHeight - paddle.h\n19 end\n20 -- snip\n

\n\n

The first return value, _crankChange, is prefixed with an underscore to signify that it’s not used. Then we take the acceleratedCrankChange variable and add it to paddle.y. This works because cranking forward returns a positive value and cranking backwards returns a negative value. Just what we need.

(debugging with print to see the crank values)

Bonus #1: swap acceleratedCrankChange for _crankChange when adding to paddle.y and see how that feels.

Bonus #2: how would you increase or decrease the crank change to refine the paddle movement?

Displaying the Ball

Similar to how we drew a rectangle for the paddle, we’ll draw a circle to represent the ball.

At the very top of source/main.lua, we need to import the graphics core library. We’ll also set up a ball table variable for tracking that data.

 1 import \"CoreLibs/graphics\"\n 2 \n 3 local paddle = {\n 4     -- snip\n 5 }\n 6 \n 7 local ball = {\n 8   x = 220,\n 9   y = 80,\n10   r = 10,\n11 }\n

\n\n

Then at the bottom of the playdate.update() function, call playdate.graphics.fillCircleAtPoint:

1 playdate.graphics.clear()\n2 playdate.graphics.fillRect(paddle.x, paddle.y, paddle.w, paddle.h)\n3 playdate.graphics.fillCircleAtPoint(ball.x, ball.y, ball.r)\n

\n\n

r represents the radius of the circle in pixels.

Bonus: Adjust the r radius of the circle to find a size that seems appropriate.

Refactoring `playdate.graphics`\n

Let’s take a brief moment to refactor our calls to playdate.graphics to follow the best practices suggested by the Playdate SDK.

We’ll introduce a constant value called gfx to make our code a bit more concise. It also makes our code slightly faster. Win-win!

Update the top of source/main.lua to add the following line below the graphics import:

1 import \"CoreLibs/graphics\"\n2 \n3 local gfx <const> = playdate.graphics\n

\n\n

<const> means that the value is constant. It shouldn’t change nor be reassigned.

Then in playdate.update() replace playdate.graphics with gfx:

1 gfx.clear()\n2 gfx.fillRect(paddle.x, paddle.y, paddle.w, paddle.h)\n3 gfx.fillCircleAtPoint(ball.x, ball.y, ball.r)\n

\n\n

Moving the Ball

We’ve coded two moving objects already—the text from Chapter 1 and the paddle in our tennis game. They responded to user input via the d-pad and crank. The ball in Tennis will move automatically. Instead of checking for player input, we’ll just modify the ball’s position in each update of the game loop.

In source/main.lua below the paddle boundary checking and above the drawing, increase the ball’s x position by 2 pixels every loop:

1 -- snip\n2 if paddle.y + paddle.h >= displayHeight then\n3   paddle.y = displayHeight - paddle.h\n4 end\n5 \n6 ball.x += 2\n7 \n8 gfx.clear()\n9 -- snip\n

\n\n

Run the game and see what happens. The ball moves to the right. Going, going, gone! It disappears off the screen. It’s still moving, deep into space. We just can’t see it.

Bonus: Refactor the code to put the ball’s speed of 2 into the ball table.

Bounce Off the Wall

Much like how we check for the top and bottom of the screen to stop moving the paddle, we’ll check to see if the ball has hit the right side of the screen. If it has, then we’ll change its direction.

 1 -- snip\n 2 \n 3 local ball = {\n 4   x = 220,\n 5   y = 80,\n 6   r = 10,\n 7   s = 4,\n 8 }\n 9 \n10 local displayHeight = playdate.display.getHeight()\n11 local displayWidth = playdate.display.getWidth()\n12 \n13 function playdate.update()\n14   -- snip\n15 \n16   ball.x += ball.s\n17 \n18   if ball.x + ball.r >= displayWidth then\n19     ball.x = displayWidth - ball.r\n20     ball.s *= -1\n21   end\n22 \n23   if ball.x <= ball.r then\n24     ball.x = ball.r\n25     ball.s *= -1\n26   end\n27 \n28   -- snip\n29 end\n

\n\n

Quite a few changes have been made. First, s was added to the ball table to represent its speed. 2 pixels per update felt too slow, so it’s been increased to 4.

The direction is encoded in the sign of ball.s—positive means move right, negative means move left. While it’s not super clear to combine speed and direction into one variable, that’s okay, it’ll end up going away when we introduce angles.

We set a variable for the displayWidth just like we did for displayHeight but call getWidth() instead. We need it for checking the boundary of the ball.

When we change the ball.x, we use ball.s instead of the magic number from the last section. And we multiply it by -1 to change the direction. *= means multiply the value on the left by the value on the right and assign that new value to it. Multiplying by -1 changes the sign of the direction.

If the ball is moving right, we’re increasing its x value, so ball.s is positive. But if we want the ball to move to the left, we need to subtract ball.s from ball.x. By multiplying ball.s by -1, it subtracts 4 from ball.x in future loops. To make the ball move right again, multiply it by -1 to turn it positive. This directional modifier is quite powerful and a regular staple of game programming.

Then we check if the ball’s x position plus its radius (r) are greater than or equal to the width of the screen. If it is, we set the ball’s position to the furthest right edge and change the direction to -1 so it moves to the left in the next game loop call of playdate.update().

Similarly but for the left side of the screen, we check if the ball.x is less than or equal to the ball’s radius (r). If it is, we set the ball.x to the ball.r and change the direction to move to the right.

The boundary checking for the ball is slightly different than our paddle as the origin point of the circle is in the center, not the upper left. This means we need to factor this into our logic. Try changing if ball.x <= ball.r then to if ball.x <= 0 then and see what happens. (And then undo it because it’s not what we want moving forward).

While it’s fun to watch the ball move back and forth, it flies right through our paddle. Let’s make it so that when the ball overlaps with the paddle, it changes direction.

Bounce Off the Paddle

To bounce the ball off of the paddle, we’ll check to see if the circular ball overlaps the rectangular paddle. This is where we introduce non-trivial math into our game in the form of trigonometry. Don’t worry if you don’t know much trig, I’ll break it down and explain it.

We’ll also introduce our first custom function to encapsulate the logic. Our playdate.update() function is getting a bit long and unwieldy, so by putting code into functions, we can keep it clear and focused.

 1 -- snip\n 2 function playdate.update()\n 3   -- snip\n 4 \n 5   ball.x += ball.s\n 6 \n 7   if circleOverlapsRect(ball, paddle) then\n 8     ball.s *= -1\n 9   end\n10 \n11   -- snip\n12 end\n13 \n14 function circleOverlapsRect(circle, rect)\n15     -- Find the closest point in the rectangle to the circle's center\n16     local closestX = math.max(rect.x, math.min(circle.x, rect.x + rect.w))\n17     local closestY = math.max(rect.y, math.min(circle.y, rect.y + rect.h))\n18 \n19     -- Calculate the distance between the circle's center and the closest point\n20     local distance = math.sqrt((closestX - circle.x)^2 + (closestY - circle.y)^2)\n21 \n22     -- If the distance is less than or equal to the radius, there's overlap\n23     return distance <= circle.r\n24 end\n

\n\n

Right below where we update the ball’s x position we’ll add a conditional check with the new function we’re adding: circleOverlapsRect. We pass in the ball (our circle) as the first parameter and then the paddle (our rectangle) as the second parameter. If the circle does overlap the rectangle, meaning the ball hit our paddle, we’ll flip the ball’s direction by changing the sign of its speed.

The circleOverlapsRect function takes a circle and rect as arguments. There are some comments that start with -- to explain the code a bit.

Let’s breakdown the determination of closestX and closestY. It checks to see what point within the rect is closest to the circle by comparing the center of the circle to the bounding box of the rect.

The distance formula is then used to determine the distance between the closest point in the rect and the center of the circle. If the distance is less than or equal to the circle’s radius (circle.r), then it means the circle is overlapping the rectangle.

Refactor into Functions

Our code in playdate.update() is getting complex and unwieldy. Let’s refactor the code we’ve got into separate functions that we call from within playdate.update(). Putting code into functions serves three key purposes:

\nFunctions help us reuse code rather than repeating it multiple times.\n
\nFunctions break our code down into smaller parts which are easier to understand.\n
\nFunctions self-document our code by grouping lines together into something with a name.\n

Our current source/main.lua looks like this:

 1 import \"CoreLibs/graphics\"\n 2 \n 3 local gfx <const> = playdate.graphics\n 4 \n 5 local paddle = {\n 6   x = 36,\n 7   y = 80,\n 8   s = 10,\n 9   w = 12,\n10   h = 48,\n11 }\n12 \n13 local ball = {\n14   x = 220,\n15   y = 80,\n16   r = 10,\n17   s = 6,\n18 }\n19 \n20 local displayHeight = playdate.display.getHeight()\n21 local displayWidth = playdate.display.getWidth()\n22 \n23 function playdate.update()\n24   if playdate.buttonIsPressed(playdate.kButtonUp) then\n25     paddle.y -= paddle.s\n26   end\n27 \n28   if playdate.buttonIsPressed(playdate.kButtonDown) then\n29     paddle.y += paddle.s\n30   end\n31 \n32   local _crankChange, acceleratedCrankChange = playdate.getCrankChange()\n33   paddle.y += acceleratedCrankChange\n34 \n35   if paddle.y <= 0 then\n36     paddle.y = 0\n37   end\n38 \n39   if paddle.y + paddle.h >= displayHeight then\n40     paddle.y = displayHeight - paddle.h\n41   end\n42 \n43   ball.x += ball.s\n44 \n45   if ball.x + ball.r >= displayWidth then\n46     ball.x = displayWidth - ball.r\n47     ball.s *= -1\n48   end\n49 \n50   if ball.x <= ball.r then\n51     ball.x = ball.r\n52     ball.s *= -1\n53   end\n54 \n55   if circleOverlapsRect(ball, paddle) then\n56     ball.s *= -1\n57   end\n58 \n59   gfx.clear()\n60   gfx.fillRect(paddle.x, paddle.y, paddle.w, paddle.h)\n61   gfx.fillCircleAtPoint(ball.x, ball.y, ball.r)\n62 end\n63 \n64 function circleOverlapsRect(circle, rect)\n65   -- Find the point to the circle center within the rectangle\n66   local closestX = math.max(rect.x, math.min(circle.x, rect.x + rect.w))\n67   local closestY = math.max(rect.y, math.min(circle.y, rect.y + rect.h))\n68 \n69   -- Distance between the circle center and the closest point\n70   local distance = math.sqrt((closestX - circle.x)^2 + (closestY - circle.y)^2)\n71 \n72   -- If the distance is less than or equal to the radius, there's overlap\n73   return distance <= circle.r\n74 end\n

\n\n

I see three functions we can extract:

\nMoving the paddle: movePaddle()\n
\nMoving the ball: moveBall()\n
\nDrawing our shapes: draw()\n

Here’s what our refactored code looks like:

 1 import \"CoreLibs/graphics\"\n 2 \n 3 local gfx <const> = playdate.graphics\n 4 \n 5 local paddle = {\n 6   x = 36,\n 7   y = 80,\n 8   s = 10,\n 9   w = 12,\n10   h = 48,\n11 }\n12 \n13 local ball = {\n14   x = 220,\n15   y = 80,\n16   r = 10,\n17   s = 6,\n18 }\n19 \n20 local displayHeight = playdate.display.getHeight()\n21 local displayWidth = playdate.display.getWidth()\n22 \n23 function playdate.update()\n24   movePaddle()\n25   moveBall()\n26 \n27   if circleOverlapsRect(ball, paddle) then\n28     ball.s *= -1\n29   end\n30 \n31   draw()\n32 end\n33 \n34 function draw()\n35   gfx.clear()\n36   gfx.fillRect(paddle.x, paddle.y, paddle.w, paddle.h)\n37   gfx.fillCircleAtPoint(ball.x, ball.y, ball.r)\n38 end\n39 \n40 function movePaddle()\n41   if playdate.buttonIsPressed(playdate.kButtonUp) then\n42     paddle.y -= paddle.s\n43   end\n44 \n45   if playdate.buttonIsPressed(playdate.kButtonDown) then\n46     paddle.y += paddle.s\n47   end\n48 \n49   local _crankChange, acceleratedCrankChange = playdate.getCrankChange()\n50   paddle.y += acceleratedCrankChange\n51 \n52   if paddle.y <= 0 then\n53     paddle.y = 0\n54   end\n55 \n56   if paddle.y + paddle.h >= displayHeight then\n57     paddle.y = displayHeight - paddle.h\n58   end\n59 end\n60 \n61 function moveBall()\n62   ball.x += ball.s\n63 \n64   if ball.x + ball.r >= displayWidth then\n65     ball.x = displayWidth - ball.r\n66     ball.s *= -1\n67   end\n68 \n69   if ball.x <= ball.r then\n70     ball.x = ball.r\n71     ball.s *= -1\n72   end\n73 end\n74 \n75 function circleOverlapsRect(circle, rect)\n76   -- Find the point to the circle center within the rectangle\n77   local closestX = math.max(rect.x, math.min(circle.x, rect.x + rect.w))\n78   local closestY = math.max(rect.y, math.min(circle.y, rect.y + rect.h))\n79 \n80   -- Distance between the circle center and the closest point\n81   local distance = math.sqrt((closestX - circle.x)^2 + (closestY - circle.y)^2)\n82 \n83   -- If the distance is less than or equal to the radius, there's overlap\n84   return distance <= circle.r\n85 end\n

\n\n

All we’ve done is move our code into separate functions and then call them within playdate.update(). It’s a lot easier to reason about and refer to the code.

The call to the circleOverlapsRect function did not get moved into its own function because it’s simple enough to just stay put. It wouldn’t fit naturally into movePaddle() or moveBall() since it deals with both of them. If collision detection gets more complicated, then it might make sense to move it into its own function.

Now that our code is cleaned up a bit, let’s make the game more exciting. Let’s introduce angles to make the ball bounce all over the screen.

Angles

Our ball is just moving along the x-axis, which isn’t very exciting. We want to make our ball move all over the screen. This means, yes, more math! We need to keep track of the angle of our ball and use that in conjunction with our speed to determine its velocity.

 1 -- snip\n 2 \n 3 local ball = {\n 4   x = 220,\n 5   y = 80,\n 6   r = 10,\n 7   s = 6,\n 8   a = 195, -- degrees\n 9 }\n10 \n11 -- snip\n12 \n13 function playdate.update()\n14   movePaddle()\n15   moveBall()\n16 \n17   if circleOverlapsRect(ball, paddle) then\n18     ball.a = math.random(160, 200) - ball.a\n19   end\n20 \n21   draw()\n22 end\n23 \n24 function draw()\n25   -- snip\n26 end\n27 \n28 function movePaddle()\n29   -- snip\n30 end\n31 \n32 function moveBall()\n33   local radians = math.rad(ball.a)\n34   ball.x += math.cos(radians) * ball.s\n35   ball.y += math.sin(radians) * ball.s\n36 \n37   if ball.x + ball.r >= displayWidth then\n38     ball.x = displayWidth - ball.r\n39     ball.a = 180 - ball.a\n40   end\n41 \n42   if ball.x <= ball.r then\n43     ball.x = ball.r\n44     ball.a = 180 - ball.a\n45   end\n46 \n47   if ball.y + ball.r >= displayHeight then\n48     ball.y = displayHeight - ball.r\n49     ball.a *= -1\n50   end\n51 \n52   if ball.y <= ball.r then\n53     ball.y = ball.r\n54     ball.a *= -1\n55   end\n56 end\n57 \n58 function circleOverlapsRect(circle, rect)\n59   -- snip\n60 end\n

\n\n

Play your game on the Playdate Simulator and upload to your Playdate to play test it if you haven’t yet. It’s starting to get fun!

There are some major changes in the code with how we’re handling the ball movement.

First, we introduce ball.a to represent the ball’s angle of movement. It’s in degrees and initially set to 195, which is to the right and down a little bit. (180 would be straight to the right.) We’ll use the angle when determining how to change the x and y position of the ball based on its speed.

In playdate.update() we set the ball.a to a random value between 160 and 200 degrees minus ball.a. This turns the ball around and gives it a little bit of random variance to prevent the ball from getting deadlocked in a straight line.

draw(), movePaddle(), and circleOverlapsRect() remain unchanged. But moveBall() gets entirely overhauled.

Let’s break down the two key parts:

1 local radians = math.rad(ball.a)\n2 ball.x += math.cos(radians) * ball.s\n3 ball.y += math.sin(radians) * ball.s\n

\n\n

Since the ball is moving at an angle, both its x and y position need to change based on that angle. More trigonometry!

We convert the ball’s angle to radians, which we need for working with the sine (math.sin()) and cosine (math.cos()) functions. We calculate the change in the x position based on the cosine of the angle times the ball’s speed. The y position is similar but we use sine instead. The foundation of this formula is using the unit circle to determine angular velocity.

After we change the x and y position, we check to see if the ball has collided with the top, bottom, left, and right side of the screen. For the left and right side along the x axis, we subtract the current ball.a from 180 to flip the horizontal movement. For the top and bottom collisions along the y axis, we multiply the ball.a by -1 to keep the horizontal direction the same but change the vertical direction.

Let’s make it so the ball gets faster each time it hits the paddle. This will make the game more challenging the better we get at it.

Speeding Up the Ball

To make the ball go faster, all we need to do is increase ball.s in our if circleOverlapsRect(ball, paddle) then conditional check in playdate.update().

1 -- snip\n2 \n3 if circleOverlapsRect(ball, paddle) then\n4   ball.a = math.random(160, 200) - ball.a\n5   ball.s += 1\n6 end\n7 \n8 -- snip\n

\n\n

It quickly gets out of hand and the ball moves way too fast. So let’s set a max upper speed by adding max_s to our ball table and checking to see if ball.s is beyond it.

 1 -- snip\n 2 \n 3 local ball = {\n 4   x = 220,\n 5   y = 80,\n 6   r = 10,\n 7   s = 6,\n 8   max_s = 12,\n 9   a = 195, -- degrees\n10 }\n11 \n12 -- snip\n13 \n14 function playdate.update()\n15   movePaddle()\n16   moveBall()\n17 \n18   if circleOverlapsRect(ball, paddle) then\n19     ball.a = math.random(160, 200) - ball.a\n20 \n21     if ball.s < ball.max_s then\n22       ball.s += 1\n23     end\n24   end\n25 \n26   draw()\n27 end\n28 \n29 -- snip\n

\n\n

There’s something really fun about using the crank to hit the ball around! We’re starting to get our first glimpses at the fun and joy of making games.

Score

Let’s keep track of the score for each round and reset it to zero if the ball hits the left wall. We’ll also reset the ball to its initial position, speed, and angle when the left wall is hit. We need a new variable, score, that we’ll set and draw on the screen. We’ll also keep track of the initial values we want to track for resetting the game.

 1 -- snip\n 2 \n 3 local ball = {\n 4   x = 220,\n 5   y = 80,\n 6   r = 10,\n 7   s = 6,\n 8   max_s = 12,\n 9   a = 195, -- degrees\n10 }\n11 \n12 ball.initX = ball.x\n13 ball.initY = ball.y\n14 ball.initS = ball.s\n15 ball.initA = ball.a\n16 \n17 local score = 0\n18 \n19 local displayHeight = playdate.display.getHeight()\n20 local displayWidth = playdate.display.getWidth()\n21 \n22 function playdate.update()\n23   movePaddle()\n24   moveBall()\n25 \n26   if circleOverlapsRect(ball, paddle) then\n27     ball.a = math.random(160, 200) - ball.a\n28 \n29     score += 1\n30 \n31     if ball.s < ball.max_s then\n32       ball.s += 1\n33     end\n34   end\n35 \n36   draw()\n37 end\n38 \n39 function draw()\n40   -- snip\n41   gfx.drawText(\"Score: \" .. score, displayWidth - 100, 20)\n42 end\n43 \n44 function movePaddle()\n45   -- snip\n46 end\n47 \n48 function moveBall()\n49   -- snip\n50 \n51   if ball.x <= ball.r then\n52     resetGame()\n53   end\n54 \n55     -- snip\n56 end\n57 \n58 function resetGame()\n59   score = 0\n60   ball.x = ball.initX\n61   ball.y = ball.initY\n62   ball.s = ball.initS\n63   ball.a = ball.initA\n64 end\n65 \n66 -- snip\n

\n\n

There’s nothing too new here. Lots of using the fundamentals we already learned. Except for the assigning of ball.initX, ball.initY, etc. Basically what the code does is that after we create the ball, we take the values and assign them to a separate entry in the table. Because ball.x, ball.y, etc. are going to change throughout the game. We want to be able to easily reset to those initial values.

We’re almost done with Tennis. Let’s polish it up a little bit more.

Sound Effects

Our game is feeling a bit quiet, don’t you think? The Playdate SDK offers a lot of options for playing sound effects, from samples to files to an included synth. We’ll add some simple MIDI sound effects to our game whenever the ball hits anything.

 1 -- snip\n 2 local synth = playdate.sound.synth.new(playdate.sound.kWaveSine)\n 3 \n 4 function playdate.update()\n 5   movePaddle()\n 6   moveBall()\n 7 \n 8   if circleOverlapsRect(ball, paddle) then\n 9     ball.a = math.random(160, 200) - ball.a\n10     playSFX(\"C4\")\n11 \n12     score += 1\n13 \n14     -- snip\n15   end\n16 \n17   draw()\n18 end\n19 \n20 function draw()\n21   -- snip\n22 end\n23 \n24 function movePaddle()\n25   -- snip\n26 end\n27 \n28 function moveBall()\n29     -- snip\n30 \n31   if ball.x + ball.r >= displayWidth then\n32     playSFX(\"E4\")\n33     ball.x = displayWidth - ball.r\n34     ball.a = 180 - ball.a\n35   end\n36 \n37   if ball.x <= ball.r then\n38     playSFX(\"F3\")\n39     resetGame()\n40   end\n41 \n42   if ball.y + ball.r >= displayHeight then\n43     playSFX(\"D4\")\n44     ball.y = displayHeight - ball.r\n45     ball.a *= -1\n46   end\n47 \n48   if ball.y <= ball.r then\n49     playSFX(\"A4\")\n50     ball.y = ball.r\n51     ball.a *= -1\n52   end\n53 end\n54 \n55 function resetGame()\n56   -- snip\n57 end\n58 \n59 function playSFX(note)\n60   synth:playMIDINote(note, 1, 0.25)\n61 end\n62 \n63 -- snip\n

\n\n

We create a new synth variable using the kWaveSine constant. And we use that in the new playSFX function, which takes a note and plays it on the synth for a quarter of a second. The second parameter, 1, is the volume of the sound effect. You can see that for each wall the ball hits, we play a different note. This is more pleasing than repeating the same sound over and over. And the sound when the ball hits the paddle is also different.

Bonus: Similar to how we greeted a random name in the first chapter, create a table of music notes and randomly select one when the ball hits the paddle.

Final Code

That’s Tennis! Our version is complete, at least for now. We learned a whole lot in this chapter. We wrote our own functions, drew shapes, implemented angular velocity, created and changed a whole bunch of variables, and made something that’s a little fun. Nice work.

Here’s the finished code for this chapter:

  1 import \"CoreLibs/graphics\"\n  2 \n  3 local gfx <const> = playdate.graphics\n  4 \n  5 local paddle = {\n  6   x = 36,\n  7   y = 80,\n  8   s = 10,\n  9   w = 12,\n 10   h = 48,\n 11 }\n 12 \n 13 local ball = {\n 14   x = 220,\n 15   y = 80,\n 16   r = 10,\n 17   s = 6,\n 18   max_s = 12,\n 19   a = 195, -- degrees\n 20 }\n 21 \n 22 ball.initX = ball.x\n 23 ball.initY = ball.y\n 24 ball.initS = ball.s\n 25 ball.initA = ball.a\n 26 \n 27 local score = 0\n 28 \n 29 local displayHeight = playdate.display.getHeight()\n 30 local displayWidth = playdate.display.getWidth()\n 31 local synth = playdate.sound.synth.new(playdate.sound.kWaveSine)\n 32 \n 33 function playdate.update()\n 34   movePaddle()\n 35   moveBall()\n 36 \n 37   if circleOverlapsRect(ball, paddle) then\n 38     ball.a = math.random(160, 200) - ball.a\n 39     playSFX(\"C4\")\n 40 \n 41     score += 1\n 42 \n 43     if ball.s < ball.max_s then\n 44       ball.s += 1\n 45     end\n 46   end\n 47 \n 48   draw()\n 49 end\n 50 \n 51 function draw()\n 52   gfx.clear()\n 53   gfx.fillRect(paddle.x, paddle.y, paddle.w, paddle.h)\n 54   gfx.fillCircleAtPoint(ball.x, ball.y, ball.r)\n 55   gfx.drawText(\"Score: \" .. score, displayWidth - 100, 20)\n 56 end\n 57 \n 58 function movePaddle()\n 59   if playdate.buttonIsPressed(playdate.kButtonUp) then\n 60     paddle.y -= paddle.s\n 61   end\n 62 \n 63   if playdate.buttonIsPressed(playdate.kButtonDown) then\n 64     paddle.y += paddle.s\n 65   end\n 66 \n 67   local _crankChange, acceleratedCrankChange = playdate.getCrankChange()\n 68   paddle.y += acceleratedCrankChange\n 69 \n 70   if paddle.y <= 0 then\n 71     paddle.y = 0\n 72   end\n 73 \n 74   if paddle.y + paddle.h >= displayHeight then\n 75     paddle.y = displayHeight - paddle.h\n 76   end\n 77 end\n 78 \n 79 function moveBall()\n 80   local radians = math.rad(ball.a)\n 81   ball.x += math.cos(radians) * ball.s\n 82   ball.y += math.sin(radians) * ball.s\n 83 \n 84   if ball.x + ball.r >= displayWidth then\n 85     playSFX(\"E4\")\n 86     ball.x = displayWidth - ball.r\n 87     ball.a = 180 - ball.a\n 88   end\n 89 \n 90   if ball.x <= ball.r then\n 91     playSFX(\"F3\")\n 92     resetGame()\n 93   end\n 94 \n 95   if ball.y + ball.r >= displayHeight then\n 96     playSFX(\"D4\")\n 97     ball.y = displayHeight - ball.r\n 98     ball.a *= -1\n 99   end\n100 \n101   if ball.y <= ball.r then\n102     playSFX(\"A4\")\n103     ball.y = ball.r\n104     ball.a *= -1\n105   end\n106 end\n107 \n108 function resetGame()\n109   score = 0\n110   ball.x = ball.initX\n111   ball.y = ball.initY\n112   ball.s = ball.initS\n113   ball.a = ball.initA\n114 end\n115 \n116 function playSFX(note)\n117   synth:playMIDINote(note, 1, 0.25)\n118 end\n119 \n120 function circleOverlapsRect(circle, rect)\n121   -- Find the point to the circle center within the rectangle\n122   local closestX = math.max(rect.x, math.min(circle.x, rect.x + rect.w))\n123   local closestY = math.max(rect.y, math.min(circle.y, rect.y + rect.h))\n124 \n125   -- Distance between the circle center and the closest point\n126   local distance = math.sqrt((closestX - circle.x)^2 + (closestY - circle.y)^2)\n127 \n128   -- If the distance is less than or equal to the radius, there's overlap\n129   return distance <= circle.r\n130 end\n

\n\n

130 lines of code. That’s respectable for our first Playdate game. If you’ve got someone you can share your Playdate with, show them what you made!

Extra Credits

There’s a lot you could do to expand Tennis into something more fun. Here are some ideas to take it to the next level:

\nMake the game two player by introducing another paddle. Player 1 controls the left paddle with the d-pad and Player 2 controls the right paddle with the crank.\n
\nAdd multiple balls that spawn after reaching certain score thresholds!\n
\nAdd collectibles to aim for or even bricks to break.\n
\nAdd pinball-style bumpers that the ball can hit.\n
\nMake the ball appear larger when it hits the paddle or a wall.\n
\nShake the paddle when it’s hit by the ball.\n
\nThere’s a small bug—sometimes the ball and paddle can get stuck on each other. How would you separate them when they collide based on the position of the ball when it hits the paddle?\n
\nIn future chapters we’ll learn about saving data. Make it so that the high score is saved between play sessions. When a new high-score is reached, modify the score text to let the player know!\n
\nAdding a mute setting would be nice!\n
\nRework the paddle’s movement to use acceleration and factor its current velocity into the angle the ball is bounced off at (e.g., if the paddle hits the ball while the paddle is moving up, the ball should also move up and to the right).\n

What’s Next

Tennis was a lot to soak in. Let’s take a breather by coding up a simple little utility for our Playdate: a clock.

Clock

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Drawing the Time

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Respecting Preferences

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Padding Zeroes

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Lowering the Framerate

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Showing Power Details

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Custom Font

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Finished Source Code

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Extra Credits

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What’s Next

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Snake

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Moving on the Grid

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Control the Snake

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Spawning Apples

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Adding Snake Pieces

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Don’t Spawn an Apple on the Snake

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Game Over

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Restart the Game

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High-Score

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Reset High-Score

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Finished Source Code

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Extra Credits

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What’s Next

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Soaring

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Controlling the Bird

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Spawning Trees

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Crank Indicator

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Scenes

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Refactoring Gameplay Reset

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Introducing a State Table

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Breaking Our Code Into Multiple Files

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Extra Credits

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

What’s Next

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Sokoban

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Moveable Player

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Pushing a Box

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Target Spot

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Counting Steps

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Preparing for Complexity

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Multiple Boxes

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Parsing Levels

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Level Select

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Extra Credits

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

What’s Next

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Dungeon Crawler - Part 1

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Drawing Player from a Tilemap

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Designing Levels with Tiled and Rendering Them

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Player Movement with Camera

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Map Collision Detection

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Talking to NPCs

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Extra Credits

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What’s Next

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Dungeon Crawler - Part 2

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Organizing Our Code

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Multiple Maps with Stairs

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Random Encounters

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Combat

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Defining Enemies

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Setting Up for Combat

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Initializing Combat

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Drawing the Combat Screen

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\nThis content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

The Message Queue

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Updating and Drawing Combat

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Player Stats & Enemy Attacks Back

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Death

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Extra Credits

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What’s Next

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Playdate by Example

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Text

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Use a Font

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Audio

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Play a Sound Effect from WAV File

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Creating a Sound Effect Table Module

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Debugging

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Capturing Gameplay Footage

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Release Steps

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Outro

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Start Small

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Releasing Your Playdate Games

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Continue to Learn

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Backing Up Your Games

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Beyond Playdate

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Game Development Tools

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Assets

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Thanks & Credit

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Playdate Cheatsheet

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System

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Display

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Draw Text

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Import Files

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Input Handling

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Sprites

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Graphics

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Images

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Timers

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Sound

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Save Data

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Animation

Lifecycle Callbacks

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Coroutines in playdate.update()

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Common Patterns

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Game State Management

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Simple Animation

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Collision Detection

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Camera/Scrolling

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Quick Constants Reference

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Lua Cheatsheet

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Variables

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Variable Types

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Multiple Assignment

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Functions

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Local Functions

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Anonymous Functions

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Functions with Multiple Returns

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Variable Arguments

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Tables

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Create Tables

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Access Table Values

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Add to a Table

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Remove from Table

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Iterate Through Tables

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Table Length

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Strings

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String Creation

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String Concatenation

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String Methods

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String Formatting

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String Patterns

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Control Flow

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If Statements

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Logical Operators

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Loops

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Operators

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Arithmetic

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Comparison

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Assignment Shortcuts

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Common Patterns

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Default Values

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Table as Object

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Error Handling

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Module Pattern

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Useful Built-in Functions

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Math

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Important Playdate Notes

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Type Checking

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Conversion

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Coroutines

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Basic Coroutine Usage

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Coroutine Status

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Passing Values

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Common Coroutine Patterns

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Playdate-Specific Coroutine Usage

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Style Guide

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Lua Styles

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n

Project Structure

This content is not available in the sample book. The book can be purchased on Leanpub at https://leanpub.com/playdatebook.\n\n

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Style Guide

Lua Styles

Project Structure

Table of Contents

Introduction

Feedback

What to Expect

Getting the Most Out of the Book

Getting Started

Installing the SDK

Setting Up the Environment Variable

Your Code Editor

Setting Up Visual Studio Code for Playdate

Next Steps

Hello, Playdate!

Counting Frames

Moving the Text

Player Input to Change Greeting

A Gentle Introduction

Tennis

Displaying the Paddle

Moving the Paddle

Displaying the Ball

Refactoring playdate.graphics\n

Moving the Ball

Bounce Off the Wall

Bounce Off the Paddle

Refactor into Functions

Angles

Speeding Up the Ball

Score

Sound Effects

Final Code

Extra Credits

What’s Next

Clock

Drawing the Time

Respecting Preferences

Padding Zeroes

Lowering the Framerate

Showing Power Details

Custom Font

Finished Source Code

Extra Credits

What’s Next

Snake

Moving on the Grid

Control the Snake

Spawning Apples

Adding Snake Pieces

Don’t Spawn an Apple on the Snake

Game Over

Restart the Game

High-Score

Reset High-Score

Finished Source Code

Extra Credits

What’s Next

Soaring

Controlling the Bird

Spawning Trees

Crank Indicator

Scenes

Refactoring Gameplay Reset

Introducing a State Table

Breaking Our Code Into Multiple Files

Extra Credits

What’s Next

Sokoban

Moveable Player

Pushing a Box

Target Spot

Counting Steps

Preparing for Complexity

Multiple Boxes

Parsing Levels

Level Select

Extra Credits

What’s Next

Dungeon Crawler - Part 1

Refactoring `playdate.graphics`\n