Ensure bird doesn't fly up too far

src/application.js

@@ -552,6 +552,12 @@ Promise.all([
 			birb.setAnimation(Animations.STILL);
 		}
 
+		// Clamp startY, birdY, targetY to a bit above the top of the window
+		const maxY = getWindowHeight() * 1.5;
+		startY = Math.min(startY, maxY);
+		birdY = Math.min(birdY, maxY);
+		targetY = Math.min(targetY, maxY);
+
 		// Update HTML element position
 		birb.setX(birdX);
 		birb.setY(birdY);