Configurable resolution

[tasuki]

Fixes #195

This is still a work in progress ⚠️ 🚧 but I'm looking for your comments!

[akx]

Quick initial comment before I look through all of this:

Based on

$ ag -o "scr_._size\s*/\s*\d+" | grep : | cut -f3 -d: | sort | uniq -c | sort -nr
  45 scr_x_size/2
  32 scr_x_size / 2
  12 scr_y_size / 20
  10 scr_y_size / 2
   8 scr_x_size / 20
   5 scr_x_size/4

it would probably make sense to at least introduce the variables scr_x_half_size and scr_y_half_size, so as to

• make the intent clearer where these are being used
• avoid two different whitespace "spellings" of the division
• (and to avoid the extra runtime divisions, not that that matters on modern hardware)

[tasuki]

I actually used to have a scr_x_half_size variable and decided to delete it because in the end I found it less readable. (I also added a scr_x_quarter_size and that made things even worse. And then there's the dividing by 20. There are so many magic numbers!)

The right solution would imo be to build up more powerful abstractions: a lot of the DRAW.CPP file is just copy-paste of the same logic, with minor variations. I don't feel competent to do that, though I guess soon enough a LLM will be able to help!