I was in the same boat last night @Tonygo2 , so I tried to document it here.
What pins are buttons/switches A, B, X and Y connected to?
They’ve now put a pinout diagram on the shop page, which says 16,17,19 and 20. RGB is 10,11 and 12.
Where can I find the syntax for the graphics commands?
As far as I can see I got them all in the documentation I linked. Let me know if anything isn’t clear.
I assume you can draw more than filled circles. (Single pixels, lines, rectangles, filled and outline?)
Single pixels, filled circles, filled squares, and single-pixel horizontal lines for now, though on the Git repo they’re talking about expanding it I think.
How do you put text on the screen? Can you change the size and colour?
Yes and yes! Again, check the docs, happy to clarify anything.
I’m afraid I’ve not looked into the Explorer yet, I don’t have one.
EDIT: The breakout ports on the Explorer are for Pimoroni’s Breakout Garden series of boards, you’ll probably need to wait until the drivers for those get updated.