OSD visualisation for addon

I am writing a video exercise addon. It basically plays a set of randomly selected (tagged) dance exercise videos from the music video library. I want to add a progress bar, both showing the progress of the current video and of the progress of the playlist plus other meta data such as elapsed time, time remaining, time to next break, difficulty level of the current dance (read from the tags), etc. The indicators must be non intrusive, e.g placed at the bottom corner of the screen.

I know python and C++, but I don't know kodi. Are there already overlays that can be tweaked to do what I want? Where do I find them? Documentation? Examples?