Note that this example is set up to use the straightforward "PIL" renderer - without the special SBB artwork!
The agent observations are displayed as squares of varying sizes, with a paler version of the agent colour. The targets are half-size squares in the full agent colour.
You can switch to the "PILSVG" renderer which is prettier but currently renders the agents one step behind, because it needs to know which way the agent is turning. This can be confusing if you are debugging step-by-step.
The image below is what the separate window should look like.