I've now implemented a basic re-usable system for creating, displaying and closing screens/dialogs.

This basic system will be used for the "load level" functionality I'm working on right now.
The general implementation enables me to easily create a screen with a functional close button.

The next step is to populate this screen with a list of levels to choose from.
For this I can re-use the system I made for displaying the tiles in the tile editor. I do need to create custom blocks of text (with maybe an image?) to display the level information that will be listed.