diff --git a/nvim/after/ftplugin/diff.vim b/nvim/after/ftplugin/diff.vim
new file mode 100644
index 0000000..ab49c88
--- /dev/null
+++ b/nvim/after/ftplugin/diff.vim
@@ -0,0 +1 @@
+setlocal nofoldenable foldmethod=manual
diff --git a/nvim/after/ftplugin/markdown.vim b/nvim/after/ftplugin/markdown.vim
index 5408829..f5408c0 100644
--- a/nvim/after/ftplugin/markdown.vim
+++ b/nvim/after/ftplugin/markdown.vim
@@ -2,9 +2,10 @@ source <sfile>:h/text.vim
 
 let s:src_file = expand('%')
 let s:out_file = s:src_file.'.html'
-let &l:makeprg = 'markdown2htmldoc '.shellescape(s:src_file).' '.shellescape(s:out_file)
+let &l:makeprg = 'markdown2htmldoc'
 for s:arg in get(g:, 'dotfiles_markdown2htmldoc_options', [])
   let &l:makeprg .= ' '.shellescape(s:arg)
 endfor
+let &l:makeprg .= ' -- '.shellescape(s:src_file).' '.shellescape(s:out_file)
 
 nnoremap <buffer> <F5> <Cmd>Open %.html<CR>
diff --git a/nvim/after/ftplugin/sass.vim b/nvim/after/ftplugin/sass.vim
new file mode 100644
index 0000000..6e88f83
--- /dev/null
+++ b/nvim/after/ftplugin/sass.vim
@@ -0,0 +1 @@
+source <sfile>:h/scss.vim
diff --git a/nvim/after/ftplugin/scss.vim b/nvim/after/ftplugin/scss.vim
index 94b3fea..9d5f7f1 100644
--- a/nvim/after/ftplugin/scss.vim
+++ b/nvim/after/ftplugin/scss.vim
@@ -1 +1,9 @@
 source <sfile>:h/css.vim
+
+let s:src_file = expand('%')
+let s:out_file = s:src_file.'.css'
+let &l:makeprg = 'sass'
+for s:arg in get(g:, 'dotfiles_dart_sass_options', [])
+  let &l:makeprg .= ' '.shellescape(s:arg)
+endfor
+let &l:makeprg .= ' -- '.shellescape(s:src_file).':'.shellescape(s:out_file)
diff --git a/nvim/colors/dotfiles.vim b/nvim/colors/dotfiles.vim
index a48e3af..bea107b 100644
--- a/nvim/colors/dotfiles.vim
+++ b/nvim/colors/dotfiles.vim
@@ -5,7 +5,8 @@
 
   execute 'source' fnameescape(g:dotfiles_dir.'/colorschemes/out/vim.vim')
 
-  if !&termguicolors && exists('$_COLORSCHEME_TERMINAL')
+  let s:is_gui_color = !has('win32') && !has('win64') && !has('win32unix') && has('termguicolors') && &termguicolors
+  if s:is_gui_color && exists('$_COLORSCHEME_TERMINAL')
     set notermguicolors
   endif
 
@@ -25,39 +26,45 @@
   endfunction
 
   let s:colors = g:dotfiles_colorscheme_base16_colors
-  function s:hi(group, fg, bg, attr, guisp)
-    let args = ''
+  function s:hi(group, fg, bg, attr, sp)
+    let fg = {}
+    let bg = {}
+    let attr = 'NONE'
+    let sp = {}
     if a:fg isnot ''
       let fg = s:is_number(a:fg) ? s:colors[a:fg] : {'gui': a:fg, 'cterm': a:fg}
-      let args .= ' guifg=' . fg.gui . ' ctermfg=' . fg.cterm
     endif
     if a:bg isnot ''
       let bg = s:is_number(a:bg) ? s:colors[a:bg] : {'gui': a:bg, 'cterm': a:bg}
-      let args .= ' guibg=' . bg.gui . ' ctermbg=' . bg.cterm
     endif
     if a:attr isnot ''
-      let args .= ' gui=' . a:attr . ' cterm=' . a:attr
+      let attr = a:attr
     endif
-    if a:guisp isnot ''
-      let guisp = s:is_number(a:guisp) ? s:colors[a:guisp].gui : a:guisp
-      let args .= ' guisp=' . guisp
+    if a:sp isnot ''
+      let sp = s:is_number(a:sp) ? s:colors[a:sp] : {'gui': a:sp, 'cterm': a:sp}
     endif
-    exec 'hi' a:group args
+    exec 'hi' a:group
+      \ 'guifg='.get(fg, 'gui', 'NONE') 'ctermfg='.get(fg, 'cterm', 'NONE')
+      \ 'guibg='.get(bg, 'gui', 'NONE') 'ctermbg='.get(bg, 'cterm', 'NONE')
+      \ 'gui='.(attr) 'cterm='.(attr)
+      \ 'guisp='.get(sp, 'gui', 'NONE')
   endfunction
 " }}}
 
 " General syntax highlighting {{{
 
-  call s:hi('Normal',     0x5,  0x0,    '',          '')
-  call s:hi('Italic',     0xE,  '',     'italic',    '')
-  call s:hi('Bold',       0xA,  '',     'bold',      '')
-  call s:hi('Underlined', 0x8,  '',     'underline', '')
-  call s:hi('Title',      0xD,  '',     'NONE',      '')
+  " TODO: `hi clear` ?
+
+  call s:hi('Normal',     0x5,  0x0, '',          '')
+  call s:hi('Italic',     0xE,  '',  'italic',    '')
+  call s:hi('Bold',       0xA,  '',  'bold',      '')
+  call s:hi('Underlined', 0x8,  '',  'underline', '')
+  call s:hi('Title',      0xD,  '',  '',          '')
   hi! link Directory Title
-  call s:hi('Conceal',    0xC,  'NONE', '',          '')
-  call s:hi('NonText',    0x3,  '',     '',          '')
+  call s:hi('Conceal',    0xC,  '',  '',          '')
+  call s:hi('NonText',    0x3,  '',  '',          '')
   hi! link SpecialKey Special
-  call s:hi('MatchParen', 'fg', 0x3,    '',          '')
+  call s:hi('MatchParen', 'fg', 0x3, '',          '')
 
   call s:hi('Keyword', 0xE, '', '', '')
   hi! link Statement    Keyword
@@ -78,7 +85,7 @@
   hi! link SpecialComment Comment
   call s:hi('Todo',       'bg', 0xA, 'bold', '')
   call s:hi('Function',   0xD, '', '', '')
-  call s:hi('Identifier', 0x8, '', 'none', '')
+  call s:hi('Identifier', 0x8, '', '', '')
   hi! link Variable Identifier
   " call s:hi('Include',    0xF, '', '', '')
   hi! link Include Keyword
@@ -88,30 +95,30 @@
   hi! link Delimiter NONE
   call s:hi('Special',    0xC, '', '', '')
   call s:hi('Tag',        0xA, '', '', '')
-  call s:hi('Type',       0xA, '', 'none', '')
+  call s:hi('Type',       0xA, '', '', '')
   hi! link Typedef Type
 
 " }}}
 
 " User interface {{{
 
-  call s:hi('Error',          'bg', 0x8,    '', '')
-  call s:hi('ErrorMsg',       0x8,  'NONE', '', '')
-  call s:hi('WarningMsg',     0x9,  'NONE', '', '')
-  call s:hi('TooLong',        0x8,  '',     '', '')
-  call s:hi('Debug',          0x8,  '',     '', '')
+  call s:hi('Error',          'bg', 0x8, '', '')
+  call s:hi('ErrorMsg',       0x8,  '',  '', '')
+  call s:hi('WarningMsg',     0x9,  '',  '', '')
+  call s:hi('TooLong',        0x8,  '',  '', '')
+  call s:hi('Debug',          0x8,  '',  '', '')
   hi! link CocErrorSign    Error
-  call s:hi('CocWarningSign', 'bg', 0xA,    '', '')
-  call s:hi('CocInfoSign',    'bg', 0xD,    '', '')
+  call s:hi('CocWarningSign', 'bg', 0xA, '', '')
+  call s:hi('CocInfoSign',    'bg', 0xD, '', '')
   hi! link CocHintSign     CocInfoSign
-  call s:hi('CocFadeOut',      0x3, '',     '', '')
+  call s:hi('CocFadeOut',      0x3, '',  '', '')
   hi! link CocMarkdownLink Underlined
 
   call s:hi('FoldColumn', 0xC, 0x1, '', '')
   call s:hi('Folded',     0x3, 0x1, '', '')
 
-  call s:hi('IncSearch', 0x1, 0x9, 'none', '')
-  call s:hi('Search',    0x1, 0xA, '',     '')
+  call s:hi('IncSearch', 0x1, 0x9, '', '')
+  call s:hi('Search',    0x1, 0xA, '', '')
   hi! link Substitute Search
 
   call s:hi('ModeMsg',  0xB, '',   '', '')
@@ -120,7 +127,7 @@
   call s:hi('Visual',   '',  0x2,  '', '')
   call s:hi('WildMenu', 0x1, 'fg', '', '')
 
-  call s:hi('CursorLine',   '',  0x1, 'none', '')
+  call s:hi('CursorLine',   '',  0x1, '', '')
   hi! link CursorColumn CursorLine
   call s:hi('ColorColumn',  '',  0x1, '', '')
   call s:hi('LineNr',       0x3, 0x1, '', '')
@@ -128,7 +135,7 @@
   call s:hi('QuickFixLine', '',  0x2, '', '')
 
   call s:hi('SignColumn',     0x3, 0x1, '', '')
-  call s:hi('StatusLine',     0x4, 0x1, 'none', '')
+  call s:hi('StatusLine',     0x4, 0x1, '', '')
   call s:hi('StatusLineNC',   0x3, 0x1, '', '')
   call s:hi('VertSplit',      0x2, 0x2, '', '')
   call s:hi('TabLine',        0x3, 0x1, '', '')
@@ -142,13 +149,12 @@
   hi! link ctrlsfLnumMatch ctrlsfMatch
 
   let s:spell_fg   = s:is_kitty ? ''          : 'bg'
-  let s:spell_bg   = s:is_kitty ? 'NONE'      : ''
   let s:spell_attr = s:is_kitty ? 'undercurl' : ''
-  call s:hi('SpellBad',   s:spell_fg, s:spell_bg, s:spell_attr, 0x8)
-  call s:hi('SpellLocal', s:spell_fg, s:spell_bg, s:spell_attr, 0xC)
-  call s:hi('SpellCap',   s:spell_fg, s:spell_bg, s:spell_attr, 0xD)
-  call s:hi('SpellRare',  s:spell_fg, s:spell_bg, s:spell_attr, 0xE)
-  unlet s:is_kitty s:spell_fg s:spell_bg s:spell_attr
+  call s:hi('SpellBad',   s:spell_fg, s:is_kitty ? '' : 0x8, s:spell_attr, 0x8)
+  call s:hi('SpellLocal', s:spell_fg, s:is_kitty ? '' : 0xC, s:spell_attr, 0xC)
+  call s:hi('SpellCap',   s:spell_fg, s:is_kitty ? '' : 0xD, s:spell_attr, 0xD)
+  call s:hi('SpellRare',  s:spell_fg, s:is_kitty ? '' : 0xE, s:spell_attr, 0xE)
+  unlet s:spell_fg s:spell_attr
 
   call s:hi('Sneak', 'bg', 0xB, 'bold', '')
   hi! link SneakScope Visual
diff --git a/nvim/init.vim b/nvim/init.vim
index a1911ba..fbbb72a 100644
--- a/nvim/init.vim
+++ b/nvim/init.vim
@@ -63,8 +63,17 @@ if exists(':Sleuth')
     " shiftwidth to the unreasonable value picked above, which vim-sleuth
     " internally compares with its local `s:default_shiftwidth`, sees that both
     " are the same, and proceeds to execute the indent detection algorithm.
-    " Boom, my work here is done.
-    autocmd BufEnter * let &l:shiftwidth = s:fake_default_shiftwidth | Sleuth
+    " ALSO Note how I'm not using `BufEnter` as vim-sleuth does because
+    " apparently `BufWinEnter` leads to better compatibility with the
+    " indentLine plugin and potentially less useless invocations (see the note
+    " about window splits in the docs for this event). Oh, one last thing:
+    " vim-sleuth forgets to assign the tabstop options, which I have to do as
+    " well. But anyway, boom, my work here is done.
+    autocmd BufWinEnter *
+      \  let &l:shiftwidth = s:fake_default_shiftwidth
+      \| Sleuth
+      \| let &l:tabstop = &l:shiftwidth
+      \| let &l:softtabstop = &l:shiftwidth
   augroup END
 
   " HACK: In case you are wondering why I'm using Polyglot's bundled vim-sleuth
diff --git a/nvim/plugin/editing.vim b/nvim/plugin/editing.vim
index 70ba62e..5a81cec 100644
--- a/nvim/plugin/editing.vim
+++ b/nvim/plugin/editing.vim
@@ -15,8 +15,8 @@ set commentstring=//%s
   function SetIndent(expandtab, shiftwidth)
     let &l:expandtab = a:expandtab
     let &l:shiftwidth = str2nr(a:shiftwidth)
-    let &l:tabstop = &shiftwidth
-    let &l:softtabstop = &shiftwidth
+    let &l:tabstop = &l:shiftwidth
+    let &l:softtabstop = &l:shiftwidth
   endfunction
   command -nargs=1 Indent call SetIndent(1, <q-args>)
   command -nargs=1 IndentTabs call SetIndent(0, <q-args>)
diff --git a/nvim/plugin/interface.vim b/nvim/plugin/interface.vim
index 11671da..8e357ce 100644
--- a/nvim/plugin/interface.vim
+++ b/nvim/plugin/interface.vim
@@ -123,6 +123,8 @@ endif
   nnoremap <silent> <F1>      <Cmd>Helptags<CR>
   nnoremap <silent> <leader>f <Cmd>Files<CR>
   nnoremap <silent> <leader>b <Cmd>Buffers<CR>
+  " <https://github.com/junegunn/fzf/blob/764316a53d0eb60b315f0bbcd513de58ed57a876/src/tui/tui.go#L496-L515>
+  let $FZF_DEFAULT_OPTS = '--color=16'
   let g:fzf_layout = { 'down': '~40%' }
   let g:fzf_preview_window = ['right:noborder', 'ctrl-/']
 " }}}
diff --git a/script-resources/colortest.awk b/script-resources/colortest.awk
index cf66228..6f87514 100644
--- a/script-resources/colortest.awk
+++ b/script-resources/colortest.awk
@@ -14,20 +14,24 @@ BEGIN {
   print "";
 }
 
-function print_color(color) {
-  printf "\033[48;5;%sm  \033[0m", color
+function print_color(color, idx) {
+  if (OPT_COLOR_CODES) {
+    printf "\033[1;30;48;5;%sm %02X \033[0m", color, idx;
+  } else {
+    printf "\033[48;5;%sm  \033[0m", color;
+  }
 }
 
 function test_standard_colors() {
   print "16 standard colors:";
-  for (color = 0; color < 16; color += 1) print_color(color);
+  for (color = 0; color < 16; color += 1) print_color(color, color);
   print "";
 }
 
 function test_base16_colorscheme() {
   print "base16 colorscheme:";
   split("0 18 19 8 20 7 21 15 1 16 3 2 6 4 5 17", colors, " ");
-  for (i = 1; i <= length(colors); i++) print_color(colors[i]);
+  for (i = 1; i <= length(colors); i++) print_color(colors[i], i - 1);
   print "";
 }
 
@@ -39,7 +43,8 @@ function test_6x6x6_cube() {
     for (row = 0; row < 6; row++) {
       for (block_x = 0; block_x < block_grid_w; block_x++) {
         for (col = 0; col < 6; col++) {
-          print_color(16 + col + 6*row + 6*6*block_x + block_grid_w*6*6*block_y);
+          color = col + 6*row + 6*6*block_x + block_grid_w*6*6*block_y
+          print_color(16 + color, color);
         }
       }
       print "";
@@ -50,7 +55,7 @@ function test_6x6x6_cube() {
 function test_grayscale() {
   print "grayscale from black to white in 24 steps:";
   for (color = 0; color < 24; color += 1) {
-    print_color(16 + 6*6*6 + color)
+    print_color(16 + 6*6*6 + color, color)
   }
   print "";
 }
diff --git a/scripts/colortest b/scripts/colortest
index 99f0f4b..9f5bc94 100755
--- a/scripts/colortest
+++ b/scripts/colortest
@@ -1,6 +1,6 @@
 #!/bin/sh
 
-set -e
+set -eu
 
 script_dir="$(dirname "$0")"
 
diff --git a/scripts/colortest2 b/scripts/colortest2
index 9b685c6..8a439ff 100755
--- a/scripts/colortest2
+++ b/scripts/colortest2
@@ -1,6 +1,6 @@
 #!/bin/sh
 
-set -e
+set -eu
 
 script_dir="$(dirname "$0")"
 cols="$(tput cols)"
diff --git a/scripts/colortest3 b/scripts/colortest3
new file mode 100755
index 0000000..84a2cef
--- /dev/null
+++ b/scripts/colortest3
@@ -0,0 +1,7 @@
+#!/bin/sh
+
+set -eu
+
+script_dir="$(dirname "$0")"
+
+exec awk -v OPT_COLOR_CODES=1 -f "${script_dir}/../script-resources/colortest.awk"
diff --git a/zsh/env.zsh b/zsh/env.zsh
index eca6fb0..baf1882 100644
--- a/zsh/env.zsh
+++ b/zsh/env.zsh
@@ -31,3 +31,6 @@ export JQ_COLORS="${(j.:.)jq_colors}"
 unset jq_colors
 
 export HOMEBREW_NO_AUTO_UPDATE=1
+
+# https://github.com/junegunn/fzf/blob/764316a53d0eb60b315f0bbcd513de58ed57a876/src/tui/tui.go#L496-L515
+export FZF_DEFAULT_OPTS="--color=16"