change packages, add Position class and Camera to BaseGame

lib/animation.dart

@@ -1,4 +1,4 @@
-import '../sprite.dart';
+import 'sprite.dart';
 
 class Animation {
   List<Sprite> sprites;

lib/components/animation_component.dart

@@ -1,7 +1,7 @@
 import 'dart:ui';
 
 import 'component.dart';
-import 'animation.dart';
+import 'package:flame/animation.dart';
 import '../sprite.dart';
 
 class AnimationComponent extends PositionComponent {

lib/components/component.dart

@@ -1,7 +1,8 @@
 import 'dart:math';
 import 'dart:ui';
 
-import 'package:flame/sprite.dart';
+import '../sprite.dart';
+import '../position.dart';
 import 'package:flutter/painting.dart';
 
 abstract class Component {
@@ -41,6 +42,10 @@ abstract class PositionComponent extends Component {
     canvas.translate(-width/2, -height/2);
   }
 
+  Position toPosition() {
+    return new Position(x, y);
+  }
+
   Rect toRect() {
     return new Rect.fromLTWH(x, y, width, height);
   }

lib/game.dart

@@ -6,6 +6,7 @@ import 'package:flutter/scheduler.dart';
 import 'package:flutter/widgets.dart';
 
 import 'components/component.dart';
+import 'position.dart';
 
 abstract class Game {
   void update(double t);
@@ -104,13 +105,16 @@ class GameRenderBox extends RenderBox {
 }
 
 abstract class BaseGame extends Game {
-  final List<Component> components = new List();
+
+  List<Component> components = new List();
   Size size;
+  Position camera = new Position.empty();
 
   @override
   void render(Canvas canvas) {
     canvas.save();
     components.forEach((comp) {
+      canvas.translate(-camera.x, -camera.y);
       comp.render(canvas);
       canvas.restore();
       canvas.save();

lib/position.dart

@@ -0,0 +1,7 @@
+class Position {
+  double x, y;
+
+  Position(this.x, this.y);
+
+  Position.empty() : this(0.0, 0.0);
+}