PhaserGames.com writes about getting container sizes: "How do you get the height and width of a container? If you’ve been playing around with Phaser 3 containers for a while, and are accustomed to using Phaser 2 groups, you may notice some familiar things missing. A few months ago I added some sprites to a container for building some user interface components. I needed to know the container size, so I could line things up properly and found that the width wasn’t set. Here is an example of what I mean."