Themes are not easy nor difficult to create. They can fall between the two. You can create an easy theme which falls under easy. Or a very complex theme which borders on difficult. Probably the best way to learn is by disassembling other themes.
This, and IMHO start with the default.
You'll notice there is NO wallpaper, yet all the screens will have a black background, yet you could have 3 different ones. You could create a wallpaper to denote 'something'.
Look at the 'main screen' last as that is where all the magic happens.
EVERYTHING HERE IS MY OPINION ONLY.
The BB naturally lends itself to be in 'landscape' and with my tired eyes I need clearly legible fonts. Take a cue from the fonts Microsoft and others used for cell phones and other small
devices. Microsoft used 'segoe ui' or something like that (all from my head), or like an old calculator font (LED I think). Try different sizes until they're legible for you.
Back to the default, look at the word 'settings'. Like here you'll see that 'g' drops lower than the base line and that is accounted for in the field size. You could either use all caps to take up the field space or icons instead.
You can use one field to suppress another or change what is shown. A good example is from °F to °C which would be a 'toggle'
Finally go to the main screen and from the bottom start moving everything slowly from the bottom to the working area. You'll notice alignment lines appear both horizontally and vertically. Those aid when constructing the screen. By the time you move the 'watts' value you'll see hidden fields appear. Those are conditionals. If you look up to the top, just to the right of the screen, you'll see under what conditions changes are made. I rip out/delete the 'session' (weed stuff) myself.
Once you've got the field sizes, alignment set, you can do an easy 'copy control'/'paste control' then change 'identified' field.
Conditions, Toggles, and user toggles, field sizes, are all on the main screen. Those are what to wrap your head around.
Like I've mentioned before, you can do all this learning on your 250C and take what you now understand to the BB before you begin.
