Keep a global ShapeRenderer instance rather than an instance per entity

core/src/com/me/brickbuster/BrickBuster.java

@@ -78,15 +78,15 @@ public class BrickBuster extends ApplicationAdapter {
 
 		long start_render = System.nanoTime();
 		for (Brick block : bricks) {
-			block.render();
+			block.render(sr);
 		}
 		for (PowerUp powerUp : powerUps) {
-			powerUp.render();
+			powerUp.render(sr);
 		}
 		for (Ball ball : balls) {
-			ball.render();
+			ball.render(sr);
 		}
-		paddle.render();
+		paddle.render(sr);
 
 		if (shieldActive) {
 			sr.begin(ShapeRenderer.ShapeType.Filled);