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Simple Ninja Game Demo

   In this demo you play a ninja and throw stars against invading monsters. It is a very simple game containing of only a single QML file with 150 lines of code.

   It features multi-resolution images, switching between 2 scenes, physics for collision detection, audio and animations for movement of the monsters and stars.

   This game idea and its image and audio resources are from the excellent cocos2d tutorial on Ray Wenderlich's site  http://www.raywenderlich.com/25736/how-to-make-a-simple-iphone-game-with-cocos2d-2-x-tutorial. The tutorial is written for the cocos2d-iphone version. In the cocos2d-x branch the same game is written in C++, which is added to the sources in the folder Demos/SimpleGameCocosNinja/cocos2d-x-Comparison folder.

   The very same game functionality as described in the tutorial is done with Felgo in this demo, to show how much code can be saved by using QML and Felgo Games. In fact, the same game is implemented with less than 60% of the original source code in C++! From 369 lines of code only 150 remain with with Felgo.
 import Felgo 3.0
 import QtQuick 2.0

 GameWindow {
   // the size of the Window can be changed at runtime by pressing the number keys 1-7
   // the content of the logical scene size (480x320 by default) gets scaled to the window size based on the scaleMode
   screenWidth: 960
   screenHeight: 640

   // You get free licenseKeys from https://felgo.com/licenseKey
   // With a licenseKey you can:
   //  * Publish your games & apps for the app stores
   //  * Remove the Felgo Splash Screen or set a custom one (available with the Pro Licenses)
   //  * Add plugins to monetize, analyze & improve your apps (available with the Pro Licenses)
   //licenseKey: "<generate one from https://felgo.com/licenseKey>"

   // create a licenseKey to hide the splash screen
   property bool splashFinished: false
   onSplashScreenFinished: { splashFinished = true}

   // this gets set from Monster, after it reached the player and is read by the GameOverScene to display if the player has won or lost
   property bool gameWon

   property int monstersDestroyed
   onMonstersDestroyedChanged: {
     if(monstersDestroyed > 5) {
       // you won the game, shot at 5 monsters

   // for creating entities (monsters and projectiles) at runtime dynamically
   EntityManager {
     id: entityManager
     entityContainer: scene

   BackgroundMusic {
     source: "../assets/snd/background-music-aac.wav" // will start playing automatically after loading

   Rectangle {
     anchors.fill: parent
     color: "white" // make a white background for the window

   Scene {
     id: scene
     // the "logical size" - the scene content is auto-scaled to match the GameWindow size
     width: 480
     height: 320

     PhysicsWorld {debugDrawVisible: false} // put it anywhere in the Scene, so the collision detection between monsters and projectiles can be done

     MultiResolutionImage {
       id: player
       anchors.verticalCenter: parent.verticalCenter
       source: "../assets/img/Player.png" // the correct image version is used, based on the GameWindow size

     // the elements of a component don't get created immediately, but in addTarget()
     // the EntityBase could also be put into an own qml file (e.g. Monster.qml)
     Component {
       id: monster

       EntityBase {
         entityType: "monster" // required for removing all of these entities when the game is lost

         MultiResolutionImage {
           id: monsterImage
           source: "../assets/img/Target.png"

         y: utils.generateRandomValueBetween(0, scene.height)

         NumberAnimation on x {
           from: scene.width // start at the right side
           to: -monsterImage.width // move the monster to the left side of the screen
           duration: utils.generateRandomValueBetween(2000, 4000) // vary animation duration between 2-4 seconds for the 480 px scene width
           onStopped: {
             console.debug("monster reached base - change to gameover scene because the player lost")

         BoxCollider {
           anchors.fill: monsterImage // make the collider as big as the image
           collisionTestingOnlyMode: true // use Box2D only for collision detection, move the entity with the NumberAnimation above
           fixture.onBeginContact: {

             // if the collided type was a projectile, both can be destroyed and the player gets a point
             var collidedEntity = other.getBody().target
             console.debug("collided with entity", collidedEntity.entityType)
             // monsters could also collide with other monsters because they have a random speed - alternatively, collider categories could be used
             if(collidedEntity.entityType === "projectile") {
               // remove the projectile entity
               // remove the monster
         }// BoxCollider
       }// EntityBase
     }// Component

     Component {
       id: projectile

       EntityBase {
         entityType: "projectile"

         MultiResolutionImage {
           id: monsterImage
           source: "../assets/img/Projectile.png"

         // these values can then be set when a new projectile is created in the MouseArea below
         property point destination
         property int moveDuration

         PropertyAnimation on x {
           from: player.x
           to: destination.x
           duration: moveDuration

         PropertyAnimation on y {
           from: player.y
           to: destination.y
           duration: moveDuration

         BoxCollider {
           anchors.fill: monsterImage
           collisionTestingOnlyMode: true
       }// EntityBase
     }// Component

     SoundEffect {
       id: projectileCreationSound
       source: "../assets/snd/pew-pew-lei.wav" // gets played when a projectile is created below

     MouseArea {
       anchors.fill: parent
       onReleased: {

         // see here for an explanation of this code: http://www.raywenderlich.com/25736/how-to-make-a-simple-iphone-game-with-cocos2d-2-x-tutorial

         // Determinie offset of player to touch location
         var offset = Qt.point(
               mouseX - player.x,
               mouseY - player.y

         // Bail out if we are shooting down or backwards
         if(offset.x <= 0)

         // Determine where we wish to shoot the projectile to
         var realX = scene.gameWindowAnchorItem.width
         var ratio = offset.y / offset.x
         var realY = (realX * ratio) + player.y
         var destination = Qt.point(realX, realY)

         // Determine the length of how far we're shooting
         var offReal = Qt.point(realX - player.x, realY - player.y)
         var length = Math.sqrt(offReal.x*offReal.x + offReal.y*offReal.y)
         var velocity = 480 // speed of the projectile should be 480pt per second
         var realMoveDuration = length / velocity * 1000 // multiply by 1000 because duration of projectile is in milliseconds

         entityManager.createEntityFromComponentWithProperties(projectile, {"destination": destination, "moveDuration": realMoveDuration})

     }// onReleased
   }// MouseArea

   // switch to this scene, after the game was lost or won and it switches back to the gameScene after 3 seconds
   Scene {
     id: gameOverScene
     visible: false
     Text {
       anchors.centerIn: parent
       text: gameWon ? "You won :)" : "You lost"

     onVisibleChanged: {
       if(visible) {
         returnToGameSceneTimer.start()  // make the scene invisible after 3 seconds, after it got visible

     Timer {
       id: returnToGameSceneTimer
       interval: 3000
       onTriggered: {
         scene.visible = true
         gameOverScene.visible = false
   }// GameOverScene

   Timer {
     running: scene.visible == true && splashFinished // only enable the creation timer, when the gameScene is visible
     repeat: true
     interval: 1000 // a new target(=monster) is spawned every second
     onTriggered: addTarget()

   function addTarget() {
     console.debug("create a new monster")

   function changeToGameOverScene(won) {

     gameWon = won

     gameOverScene.visible = true
     scene.visible = false

     // reset the game variables and remove all projectiles and monsters
     monstersDestroyed = 0
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