Cover image for Flutter Web and Flame

Flutter Web and Flame

aseemwangoo profile image aseem wangoo ・9 min read

Article here : https://flatteredwithflutter.com/how-to-create-game-in-flutter-web-using-flame/

We will cover briefly about creating a game

  1. Using Flame
  2. This article is an overview of using Flame
  3. Detailed explanation of Flame available here.
  4. Game assets were found at OpenGameArt

Note : For learning how to create a game, step by step, please follow this. This game itself was created by following this.

Introducing Flame….

Alt Text

As per the documentation :

Flame is a minimalist Flutter game engine…

Steps :

  1. Add this to your pubspec.yaml file
dependencies:  flame: ^0.19.1

2. Create a Game class

In case of normal Flutter Apps, we tend to create a class which internally implements a MaterialApp,

but here, we define a class named GameTime that extends Flame’s Game class.

class GameTime extends Game {
  void render(Canvas canvas) {}
  void update(double t) {}

3. Overview of runApp

void main() => runApp(GameScreen());

class GameScreen extends StatefulWidget {
  const GameScreen({Key key}) : super(key: key);
  static final _game = GameTime();

  _GameScreenState createState() => _GameScreenState();

class _GameScreenState extends State {
  Widget build(BuildContext context) => GameScreen._game.widget;

This creates our page into a game !!

Notice that, GameTime class itself has a widget property.

As per the docs, widget

Returns the game widget. Put this in your structure to start rendering and updating the game. You can add it directly to the runApp method or inside your widget structure.

Our game — COVIDER !!!

Alt Text

Rules :

  1. Tap on the virus to kill..
  2. Each virus killed, you earn a point
  3. There is a time associated with each virus, failing to kill in that time, you lose
  4. Tap outside the virus, you also lose.

Play here

Basics for COVIDER

Covider, (name of our game) is divided into

  • Components
  • Controller
  • Views
  • Game Class , (GameTimeclass)

Every game requires resources, assets, variables etc to be loaded before anything else happens,

we do so by calling a function initialize inside the GameTime constructor

GameTime() {

Future<void> get initialize async {

Current size of the screen

We make use of the Flame’s utility called initialDimensions…

final _size = await Flame.util.initialDimensions();

and pass this value inside the resize function.

void resize(Size size) {
screenSize = size;

hence, at every point of time, we have the latest screensize….

Draw Background…

First, we download an asset and put inside the pubspec.yaml

- assets/images/
- assets/images/bg/room.png

Note: I had to specify the image path, to load, although I had already included the folder images

For loading images in Flame,


We have a class called AssetsLoader wherein we load assets…This is called in the initState ofGameScreen ..

class _GameScreenState extends State<GameScreen> {
void initState() {

Lets create a Background Component, to separate the background’s logic…

class Background {
    @required this.gameTime,
  }) {
    bgSprite = Sprite(GameUtils.roomImage);
    bgRect = Rect.fromLTWH(
  final GameTime gameTime;

  Rect bgRect;
  Sprite bgSprite;

  void render(Canvas c) {
    bgSprite.renderRect(c, bgRect);

Sprite : From flame package, used to draw onto the screen.

In our case, we are passing the image, which we downloaded earlier, using bgSprite.

renderRect : To render the background image.

We create a rectangle, which is of the same dimensions as our screen. It takes in two parameters, canvas and the rectangle to be drawn…

Now for rendering the background inside GameTime….

  1. Initialize the instance of this component as
Background background;

and inside the GameTime initialize function, write this

background = Background(gameTime: this);

This will make sure, we always have the background instance…..

2. Inside the render method of GameTime ,

void render(Canvas canvas) {

this calls the render method of background, which we defined earlier…Your background is visible now….

Note : Pretty much each component, uses this logic….

Include Audio

We downloaded assets for hit, lose and background music, put inside the pubspec.yaml

- assets/audio/bgm/bg_music.mp3
- assets/audio/sfx/hit1.mp3
- assets/audio/sfx/hit2.mp3
- assets/audio/sfx/laugh.mp3

Just like we loaded images, we now need to load sounds in Flame…

static void loadSounds() {

where GameUtils.sounds is the list of string

Flame package comes with AudioPlayer,meaning you don’t need to add any other package…

  • Create a variable inside GameTime
AudioPlayer playBGM;
  • Inside GameTime initialize method
playBGM = await Flame.audio.loopLongAudio(GameUtils.bgMusic, volume: 0.25);

audio.loopLongAudio : allows for audios of any length to be played. We set the volume (optional param) to 0.25..

Note : This is used to play the background music

  • For one-time sounds, like hit or miss,

Flame.audio.play(GameUtils.laughSound); // LAUGH SOUND

use audio.play : makes uses of optimized features

Draw Virus

We downloaded assets for fly-up and fly-down and put inside the pubspec.yaml

- assets/images/virus/virus_fly_up.png
- assets/images/virus/virus_fly_down.png

Lets create Virus Component..

class Virus {
    @required this.gameTime,

  final GameTime gameTime;

  double get virusSpeed => gameTime.tileSize * 2;
  void render(Canvas c) {}

  void update(double t) {}

  void onTapDown() {}

  void get setupVirusLocation {}

and from this class, we created two other classes called MovingVirus and MovingDragonVirus


class MovingVirus extends Virus {
    GameTime gameTime,
    double left,
    double top,
  ) : super(gameTime: gameTime) {
    virusRect = Rect.fromLTWH(left, top, gameTime.tileSize, gameTime.tileSize);

    movingVirusSprite = <Sprite>[];

deadVirusSprite = Sprite(GameUtils.virusDead);

Basically, for any flying motion, we always have used two images -(one for fly up) and (other for fly down). Then, adding to the sprites respectively..

In order to create different speeds for viruses, we override the virusSpeed


class MovingDragonVirus extends Virus {
    GameTime gameTime,
    double left,
    double top,
  ) : super(gameTime: gameTime) {
    virusRect = Rect.fromLTWH(
        gameTime.tileSize * GameUtils.maxVirusSize,
        gameTime.tileSize * GameUtils.maxVirusSize);

    movingVirusSprite = [];

    deadVirusSprite = Sprite(GameUtils.virusDead);

  double get virusSpeed => gameTime.tileSize * 5;

Note : For the motion of virus, kindly visit here for detailed explanation.

Storing High Scores…

For storing data, we made use of dart:html , which gives access to localStorage

For accessing the localStorage,

final _localStorage = html.window.localStorage;

To visit localstorage, (screenshot from Chrome)

Alt Text

and we store the data inside it as a String….

_localStorage[‘$key’] = value;

Hosted URL : https://fir-signin-4477d.firebaseapp.com/#/

Source code for Flutter Web App..

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aseem wangoo


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