Slitherine

I am having difficulty seeing the units on the map. The manual says the + key zooms in. The only zoom I get is either the square counters or the icon which are really small and hard to distinguish what units belong to who. I am playing on a laptop without a mouse so I can't wheel in and hitting the + key doesn't seem to do anything.
How many levels of zoom in are there?
When I first fired up the game I was asked about my memory and given a choice of display type. I chose the low display as I was not sure if my computer would handle the high display. Does this have a bearing on the zoom level?

There are 3 levels. You can use the mouse wheel or the + and - keys to zoom in/out.
I'm not sure if this is related with High Display option... I don't think so. Try a mouse and see if the world with a wheel.