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CarChallenge Demo

 import QtQuick 2.0

 import Felgo 4.0

 EntityBase {
   id: entity
   entityType: "rocket"

   Component.onCompleted: {
       console.debug("Rocket.onCompleted, width:", width);
       applyForwardImpulse();
   }

   property real angleDeg

   rotation: angleDeg

   BoxCollider {
     id: boxCollider

     // the image and the physics will use this size; this is important as it specifies the mass of the body! it is in respect to the world size
     width: 50
     height: 20

     anchors.centerIn: parent

     density: 0.003
     friction: 0.4
     restitution: 0.5
     body.bullet: true
     // we prevent the physics engine from applying rotation to the rocket, because we will do it ourselves
     body.fixedRotation: true

     property var lastWall: null

     fixture.onBeginContact: (other, contactNormal) => {
       var fixture = other;
       var body = other.getBody();
       var otherEntity = body.target

       // get the entityType of the colliding entity
       var collidingType = otherEntity.entityType

       if(collidingType === "car" ||
               collidingType === "rocket") {
           entity.removeEntity()
           return
       }

       //can't hit the same wall twice, but onBeginContact called again after rotation has changed
       if(otherEntity === lastWall) {
         return;
       }
       lastWall = otherEntity

       //apply law of reflection, all calculations in degrees
       var normalAngle = 180 / Math.PI * Math.atan2(contactNormal.y, contactNormal.x)
       var angleDiff = normalAngle - entity.rotation
       var newAngle = entity.rotation + 2 * angleDiff + 180

       // manually set the entity rotation, because it is the target and its rotation will be used for the physics body
       entity.rotation = newAngle

       // it's important to clear the old velocity before applying the impulse, otherwise the rocket would get faster every time it collides with a wall!
       boxCollider.body.linearVelocity = Qt.point(0,0)

       applyForwardImpulse();
     }
   }

   Image {
     id: image
     source: Qt.resolvedUrl("../../assets/img/rocket_green.png")
     anchors.centerIn: parent
     width: boxCollider.width
     height: boxCollider.height
   }

   function applyForwardImpulse() {
     var power = 1500
     var rad = entity.rotation / 180 * Math.PI

     //can't use body.toWorldVector() because the rotation is not instantly
     var localForward = Qt.point(power * Math.cos(rad), power * Math.sin(rad))