First of all, we have a health bar. I wondered how to show the player's life ebbing away when he touches monsters. Should it be a health bar getting smaller? A simple number? Maybe a face gradually turning into a skull?
In the end I decided on the classic: hearts. And, just to make it a little different, hearts which can be split in half. See how it works in the video below.
I have also added an interactive object: a signpost. I originally created a single class of interactive objects which could be customised to behave in a number of different ways: signposts, talking people, switches, moveable blocks etc
Since then I have decided to create each type of object as a separate class. I think that will make it easier to maintain later as I add more types. The signpost type has been implemented in the video.
Finally, I worked out a simple method of layering to maintain the pseudo-3D effect of the screen. Monsters placed higher up the screen appear to be behind you, and objects lower down appear in front. This has not been applied to the other interactives, but it should not be hard to transfer the same principle.