diff --git a/autoload/limelight.vim b/autoload/limelight.vim
new file mode 100644
index 0000000..027e294
--- /dev/null
+++ b/autoload/limelight.vim
@@ -0,0 +1,245 @@
+" Copyright (c) 2015 Junegunn Choi
+"
+" MIT License
+"
+" Permission is hereby granted, free of charge, to any person obtaining
+" a copy of this software and associated documentation files (the
+" "Software"), to deal in the Software without restriction, including
+" without limitation the rights to use, copy, modify, merge, publish,
+" distribute, sublicense, and/or sell copies of the Software, and to
+" permit persons to whom the Software is furnished to do so, subject to
+" the following conditions:
+"
+" The above copyright notice and this permission notice shall be
+" included in all copies or substantial portions of the Software.
+"
+" THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+" EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+" MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+" NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+" LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+" OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+" WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+if exists('g:loaded_limelight')
+  finish
+endif
+let g:loaded_limelight = 1
+
+let s:cpo_save = &cpo
+set cpo&vim
+
+let s:default_coeff = 0.5
+let s:invalid_coefficient = 'Invalid coefficient. Expected: 0.0 ~ 1.0'
+
+function! s:unsupported()
+  let var = 'g:limelight_conceal_'.(has('gui_running') ? 'gui' : 'cterm').'fg'
+
+  if exists(var)
+    return 'Cannot calculate background color.'
+  else
+    return 'Unsupported color scheme. '.var.' required.'
+  endif
+endfunction
+
+function! s:limelight()
+  if !exists('w:limelight_prev')
+    let w:limelight_prev = [0, 0, 0, 0]
+  endif
+  if !exists('w:limelight_match_ids')
+    let w:limelight_match_ids = []
+  endif
+
+  let curr = [line('.'), line('$')]
+  if curr ==# w:limelight_prev[0 : 1]
+    return
+  endif
+
+  let paragraph = [searchpos('^$', 'bnW')[0], searchpos('^$', 'nW')[0]]
+  if paragraph ==# w:limelight_prev[2 : 3]
+    return
+  endif
+
+  call s:clear_hl()
+  call add(w:limelight_match_ids, matchadd('LimelightDim', '\%<'.paragraph[0].'l'))
+  if paragraph[1] > 0
+    call add(w:limelight_match_ids, matchadd('LimelightDim', '\%>'.paragraph[1].'l'))
+  endif
+  let w:limelight_prev = extend(curr, paragraph)
+endfunction
+
+function! s:clear_hl()
+  while !empty(w:limelight_match_ids)
+    silent! call matchdelete(remove(w:limelight_match_ids, -1))
+  endwhile
+endfunction
+
+function! s:hex2rgb(str)
+  let str = substitute(a:str, '^#', '', '')
+  return [eval('0x'.str[0:1]), eval('0x'.str[2:3]), eval('0x'.str[4:5])]
+endfunction
+
+let s:gray_converter = {
+\ 0:   231,
+\ 7:   254,
+\ 15:  256,
+\ 16:  231,
+\ 231: 256
+\ }
+
+function! s:gray_contiguous(col)
+  let val = get(s:gray_converter, a:col, a:col)
+  if val < 231 || val > 256
+    throw s:unsupported()
+  endif
+  return val
+endfunction
+
+function! s:gray_ansi(col)
+  return a:col == 231 ? 0 : (a:col == 256 ? 231 : a:col)
+endfunction
+
+function! s:coeff(coeff)
+  let coeff = a:coeff < 0 ?
+        \ get(g:, 'limelight_default_coefficient', s:default_coeff) : a:coeff
+  if coeff < 0 || coeff > 1
+    throw 'Invalid g:limelight_default_coefficient. Expected: 0.0 ~ 1.0'
+  endif
+  return coeff
+endfunction
+
+function! s:dim(coeff)
+  let synid = synIDtrans(hlID('Normal'))
+  let fg = synIDattr(synid, 'fg#')
+  let bg = synIDattr(synid, 'bg#')
+
+  if has('gui_running')
+    if a:coeff < 0 && exists('g:limelight_conceal_guifg')
+      let dim = g:limelight_conceal_guifg
+    elseif empty(fg) || empty(bg)
+      throw s:unsupported()
+    else
+      let coeff = s:coeff(a:coeff)
+      let fg_rgb = s:hex2rgb(fg)
+      let bg_rgb = s:hex2rgb(bg)
+      let dim_rgb = [
+            \ bg_rgb[0] * coeff + fg_rgb[0] * (1 - coeff),
+            \ bg_rgb[1] * coeff + fg_rgb[1] * (1 - coeff),
+            \ bg_rgb[2] * coeff + fg_rgb[2] * (1 - coeff)]
+      let dim = '#'.join(map(dim_rgb, 'printf("%x", float2nr(v:val))'), '')
+    endif
+    execute printf('hi LimelightDim guifg=%s guisp=bg', dim)
+  elseif &t_Co == 256
+    if a:coeff < 0 && exists('g:limelight_conceal_ctermfg')
+      let dim = g:limelight_conceal_ctermfg
+    elseif fg <= -1 || bg <= -1
+      throw s:unsupported()
+    else
+      let coeff = s:coeff(a:coeff)
+      let fg = s:gray_contiguous(fg)
+      let bg = s:gray_contiguous(bg)
+      let dim = s:gray_ansi(float2nr(bg * coeff + fg * (1 - coeff)))
+    endif
+    if type(dim) == 1
+      execute printf('hi LimelightDim ctermfg=%s', dim)
+    else
+      execute printf('hi LimelightDim ctermfg=%d', dim)
+    endif
+  else
+    throw 'Unsupported terminal. Sorry.'
+  endif
+endfunction
+
+function! s:error(msg)
+  echohl ErrorMsg
+  echo a:msg
+  echohl None
+endfunction
+
+function! s:parse_coeff(coeff)
+  let t = type(a:coeff)
+  if t == 1
+    if a:coeff =~ '^ *[0-9.]\+ *$'
+      let c = str2float(a:coeff)
+    else
+      throw s:invalid_coefficient
+    endif
+  elseif index([0, 5], t) >= 0
+    let c = t
+  else
+    throw s:invalid_coefficient
+  endif
+  return c
+endfunction
+
+function! s:on(...)
+  try
+    let s:limelight_coeff = a:0 > 0 ? s:parse_coeff(a:1) : -1
+    call s:dim(s:limelight_coeff)
+  catch
+    return s:error(v:exception)
+  endtry
+
+  augroup limelight
+    autocmd!
+    autocmd CursorMoved,CursorMovedI * call s:limelight()
+    autocmd ColorScheme * try
+                       \|   call s:dim(s:limelight_coeff)
+                       \|   call s:limelight()
+                       \| catch
+                       \|   call s:off()
+                       \|   throw v:exception
+                       \| endtry
+  augroup END
+
+  " FIXME: We cannot safely remove this group once Limelight started
+  augroup limelight_cleanup
+    autocmd!
+    autocmd WinEnter * call s:cleanup()
+  augroup END
+
+  doautocmd CursorMoved
+endfunction
+
+function! s:off()
+  if exists('w:limelight_match_ids')
+    call s:clear_hl()
+  endif
+  augroup limelight
+    autocmd!
+  augroup END
+  augroup! limelight
+  unlet! w:limelight_prev w:limelight_match_ids
+endfunction
+
+function! s:is_on()
+  return exists('#limelight')
+endfunction
+
+function! s:cleanup()
+  if !s:is_on() && exists('w:limelight_match_ids')
+    call s:clear_hl()
+  end
+endfunction
+
+function! limelight#execute(bang, ...)
+  if a:bang
+    if a:0 > 0 && a:1 =~ '^!' && !s:is_on()
+      if len(a:1) > 1
+        call s:on(a:1[1:-1])
+      else
+        call s:on()
+      endif
+    else
+      call s:off()
+    endif
+  elseif a:0 > 0
+    call s:on(a:1)
+  else
+    call s:on()
+  endif
+endfunction
+
+let &cpo = s:cpo_save
+unlet s:cpo_save
+
diff --git a/plugin/limelight.vim b/plugin/limelight.vim
index d338634..9bd92df 100644
--- a/plugin/limelight.vim
+++ b/plugin/limelight.vim
@@ -1,4 +1,4 @@
-" Copyright (c) 2014 Junegunn Choi
+" Copyright (c) 2015 Junegunn Choi
 "
 " MIT License
 "
@@ -21,227 +21,5 @@
 " OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 " WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
-if exists('g:loaded_limelight')
-  finish
-endif
-let g:loaded_limelight = 1
-
-let s:cpo_save = &cpo
-set cpo&vim
-
-let s:default_coeff = 0.5
-let s:invalid_coefficient = 'Invalid coefficient. Expected: 0.0 ~ 1.0'
-
-function! s:unsupported()
-  let var = 'g:limelight_conceal_'.(has('gui_running') ? 'gui' : 'cterm').'fg'
-
-  if exists(var)
-    return 'Cannot calculate background color.'
-  else
-    return 'Unsupported color scheme. '.var.' required.'
-  endif
-endfunction
-
-function! s:limelight()
-  if !exists('w:limelight_prev')
-    let w:limelight_prev = [0, 0, 0, 0]
-  endif
-  if !exists('w:limelight_match_ids')
-    let w:limelight_match_ids = []
-  endif
-
-  let curr = [line('.'), line('$')]
-  if curr ==# w:limelight_prev[0 : 1]
-    return
-  endif
-
-  let paragraph = [searchpos('^$', 'bnW')[0], searchpos('^$', 'nW')[0]]
-  if paragraph ==# w:limelight_prev[2 : 3]
-    return
-  endif
-
-  call s:clear_hl()
-  call add(w:limelight_match_ids, matchadd('LimelightDim', '\%<'.paragraph[0].'l'))
-  if paragraph[1] > 0
-    call add(w:limelight_match_ids, matchadd('LimelightDim', '\%>'.paragraph[1].'l'))
-  endif
-  let w:limelight_prev = extend(curr, paragraph)
-endfunction
-
-function! s:clear_hl()
-  while !empty(w:limelight_match_ids)
-    silent! call matchdelete(remove(w:limelight_match_ids, -1))
-  endwhile
-endfunction
-
-function! s:hex2rgb(str)
-  let str = substitute(a:str, '^#', '', '')
-  return [eval('0x'.str[0:1]), eval('0x'.str[2:3]), eval('0x'.str[4:5])]
-endfunction
-
-let s:gray_converter = {
-\ 0:   231,
-\ 7:   254,
-\ 15:  256,
-\ 16:  231,
-\ 231: 256
-\ }
-
-function! s:gray_contiguous(col)
-  let val = get(s:gray_converter, a:col, a:col)
-  if val < 231 || val > 256
-    throw s:unsupported()
-  endif
-  return val
-endfunction
-
-function! s:gray_ansi(col)
-  return a:col == 231 ? 0 : (a:col == 256 ? 231 : a:col)
-endfunction
-
-function! s:coeff(coeff)
-  let coeff = a:coeff < 0 ?
-        \ get(g:, 'limelight_default_coefficient', s:default_coeff) : a:coeff
-  if coeff < 0 || coeff > 1
-    throw 'Invalid g:limelight_default_coefficient. Expected: 0.0 ~ 1.0'
-  endif
-  return coeff
-endfunction
-
-function! s:dim(coeff)
-  let synid = synIDtrans(hlID('Normal'))
-  let fg = synIDattr(synid, 'fg#')
-  let bg = synIDattr(synid, 'bg#')
-
-  if has('gui_running')
-    if a:coeff < 0 && exists('g:limelight_conceal_guifg')
-      let dim = g:limelight_conceal_guifg
-    elseif empty(fg) || empty(bg)
-      throw s:unsupported()
-    else
-      let coeff = s:coeff(a:coeff)
-      let fg_rgb = s:hex2rgb(fg)
-      let bg_rgb = s:hex2rgb(bg)
-      let dim_rgb = [
-            \ bg_rgb[0] * coeff + fg_rgb[0] * (1 - coeff),
-            \ bg_rgb[1] * coeff + fg_rgb[1] * (1 - coeff),
-            \ bg_rgb[2] * coeff + fg_rgb[2] * (1 - coeff)]
-      let dim = '#'.join(map(dim_rgb, 'printf("%x", float2nr(v:val))'), '')
-    endif
-    execute printf('hi LimelightDim guifg=%s guisp=bg', dim)
-  elseif &t_Co == 256
-    if a:coeff < 0 && exists('g:limelight_conceal_ctermfg')
-      let dim = g:limelight_conceal_ctermfg
-    elseif fg <= -1 || bg <= -1
-      throw s:unsupported()
-    else
-      let coeff = s:coeff(a:coeff)
-      let fg = s:gray_contiguous(fg)
-      let bg = s:gray_contiguous(bg)
-      let dim = s:gray_ansi(float2nr(bg * coeff + fg * (1 - coeff)))
-    endif
-    if type(dim) == 1
-      execute printf('hi LimelightDim ctermfg=%s', dim)
-    else
-      execute printf('hi LimelightDim ctermfg=%d', dim)
-    endif
-  else
-    throw 'Unsupported terminal. Sorry.'
-  endif
-endfunction
-
-function! s:error(msg)
-  echohl ErrorMsg
-  echo a:msg
-  echohl None
-endfunction
-
-function! s:parse_coeff(coeff)
-  let t = type(a:coeff)
-  if t == 1
-    if a:coeff =~ '^ *[0-9.]\+ *$'
-      let c = str2float(a:coeff)
-    else
-      throw s:invalid_coefficient
-    endif
-  elseif index([0, 5], t) >= 0
-    let c = t
-  else
-    throw s:invalid_coefficient
-  endif
-  return c
-endfunction
-
-function! s:on(...)
-  try
-    let s:limelight_coeff = a:0 > 0 ? s:parse_coeff(a:1) : -1
-    call s:dim(s:limelight_coeff)
-  catch
-    return s:error(v:exception)
-  endtry
-
-  augroup limelight
-    autocmd!
-    autocmd CursorMoved,CursorMovedI * call s:limelight()
-    autocmd ColorScheme * try
-                       \|   call s:dim(s:limelight_coeff)
-                       \|   call s:limelight()
-                       \| catch
-                       \|   call s:off()
-                       \|   throw v:exception
-                       \| endtry
-  augroup END
-
-  " FIXME: We cannot safely remove this group once Limelight started
-  augroup limelight_cleanup
-    autocmd!
-    autocmd WinEnter * call s:cleanup()
-  augroup END
-
-  doautocmd CursorMoved
-endfunction
-
-function! s:off()
-  if exists('w:limelight_match_ids')
-    call s:clear_hl()
-  endif
-  augroup limelight
-    autocmd!
-  augroup END
-  augroup! limelight
-  unlet! w:limelight_prev w:limelight_match_ids
-endfunction
-
-function! s:is_on()
-  return exists('#limelight')
-endfunction
-
-function! s:do(bang, ...)
-  if a:bang
-    if a:0 > 0 && a:1 =~ '^!' && !s:is_on()
-      if len(a:1) > 1
-        call s:on(a:1[1:-1])
-      else
-        call s:on()
-      endif
-    else
-      call s:off()
-    endif
-  elseif a:0 > 0
-    call s:on(a:1)
-  else
-    call s:on()
-  endif
-endfunction
-
-function! s:cleanup()
-  if !s:is_on() && exists('w:limelight_match_ids')
-    call s:clear_hl()
-  end
-endfunction
-
-command! -nargs=? -bar -bang Limelight call s:do('<bang>' == '!', <f-args>)
-
-let &cpo = s:cpo_save
-unlet s:cpo_save
+command! -nargs=? -bar -bang Limelight call limelight#execute(<bang>0, <f-args>)