diff --git a/lua/mind/commands.lua b/lua/mind/commands.lua
index 71f6359..e59ccff 100644
--- a/lua/mind/commands.lua
+++ b/lua/mind/commands.lua
@@ -2,12 +2,12 @@
 
 local M = {}
 
-local mind_data = require'mind.data'
-local mind_indexing = require'mind.indexing'
-local mind_keymap = require'mind.keymap'
-local mind_node = require'mind.node'
-local mind_ui = require'mind.ui'
-local notify = require'mind.notify'.notify
+local mind_data = require("mind.data")
+local mind_indexing = require("mind.indexing")
+local mind_keymap = require("mind.keymap")
+local mind_node = require("mind.node")
+local mind_ui = require("mind.ui")
+local notify = require("mind.notify").notify
 
 M.commands = {
   toggle_node = function(args)
@@ -24,23 +24,48 @@ M.commands = {
   end,
 
   add_above = function(args)
-    M.create_node_cursor(args.get_tree(), mind_node.MoveDir.ABOVE, args.save_tree, args.opts)
+    M.create_node_cursor(
+      args.get_tree(),
+      mind_node.MoveDir.ABOVE,
+      args.save_tree,
+      args.opts
+    )
   end,
 
   add_below = function(args)
-    M.create_node_cursor(args.get_tree(), mind_node.MoveDir.BELOW, args.save_tree, args.opts)
+    M.create_node_cursor(
+      args.get_tree(),
+      mind_node.MoveDir.BELOW,
+      args.save_tree,
+      args.opts
+    )
   end,
 
   add_inside_start = function(args)
-    M.create_node_cursor(args.get_tree(), mind_node.MoveDir.INSIDE_START, args.save_tree, args.opts)
+    M.create_node_cursor(
+      args.get_tree(),
+      mind_node.MoveDir.INSIDE_START,
+      args.save_tree,
+      args.opts
+    )
   end,
 
   add_inside_end = function(args)
-    M.create_node_cursor(args.get_tree(), mind_node.MoveDir.INSIDE_END, args.save_tree, args.opts)
+    M.create_node_cursor(
+      args.get_tree(),
+      mind_node.MoveDir.INSIDE_END,
+      args.save_tree,
+      args.opts
+    )
   end,
 
   add_inside_end_index = function(args)
-    M.create_node_index(args.get_tree(), mind_node.MoveDir.INSIDE_END, args.save_tree, args.opts)
+    M.create_node_index(
+      args.get_tree(),
+      mind_node.MoveDir.INSIDE_END,
+      args.save_tree,
+      args.opts
+    )
   end,
 
   delete = function(args)
@@ -97,19 +122,39 @@ M.commands = {
   end,
 
   move_above = function(args)
-    M.move_node_selected_cursor(args.get_tree(), mind_node.MoveDir.ABOVE, args.save_tree, args.opts)
+    M.move_node_selected_cursor(
+      args.get_tree(),
+      mind_node.MoveDir.ABOVE,
+      args.save_tree,
+      args.opts
+    )
   end,
 
   move_below = function(args)
-    M.move_node_selected_cursor(args.get_tree(), mind_node.MoveDir.BELOW, args.save_tree, args.opts)
+    M.move_node_selected_cursor(
+      args.get_tree(),
+      mind_node.MoveDir.BELOW,
+      args.save_tree,
+      args.opts
+    )
   end,
 
   move_inside_start = function(args)
-    M.move_node_selected_cursor(args.get_tree(), mind_node.MoveDir.INSIDE_START, args.save_tree, args.opts)
+    M.move_node_selected_cursor(
+      args.get_tree(),
+      mind_node.MoveDir.INSIDE_START,
+      args.save_tree,
+      args.opts
+    )
   end,
 
   move_inside_end = function(args)
-    M.move_node_selected_cursor(args.get_tree(), mind_node.MoveDir.INSIDE_END, args.save_tree, args.opts)
+    M.move_node_selected_cursor(
+      args.get_tree(),
+      mind_node.MoveDir.INSIDE_END,
+      args.save_tree,
+      args.opts
+    )
   end,
 }
 
@@ -136,7 +181,7 @@ M.open_data = function(tree, node, directory, save_tree, opts)
       should_expand
     )
 
-    if (data == nil) then
+    if data == nil then
       return
     end
 
@@ -150,9 +195,9 @@ M.open_data = function(tree, node, directory, save_tree, opts)
   local winnr
   for _, tabpage_winnr in ipairs(vim.api.nvim_tabpage_list_wins(0)) do
     local bufnr = vim.api.nvim_win_get_buf(tabpage_winnr)
-    local buftype = vim.api.nvim_buf_get_option(bufnr, 'buftype')
+    local buftype = vim.api.nvim_get_option_value("buftype", { buf = bufnr })
 
-    if buftype == '' then
+    if buftype == "" then
       winnr = tabpage_winnr
       break
     end
@@ -160,23 +205,23 @@ M.open_data = function(tree, node, directory, save_tree, opts)
 
   -- pick the first window in the list; if it’s empty, we open a new one
   if winnr == nil then
-    vim.api.nvim_exec('rightb vsp ' .. data, false)
+    vim.api.nvim_exec2("rightb vsp " .. data, { output = false })
   else
     vim.api.nvim_set_current_win(winnr)
-    vim.api.nvim_exec('e ' .. data, false)
+    vim.api.nvim_exec2("e " .. data, { output = false })
   end
 
-    if opts.ui.close_on_file_open == true then
-        M.close()
-    end
+  if opts.ui.close_on_file_open == true then
+    M.close()
+  end
 end
 
 -- Delete the data file associated with a node.
 --
 -- If it doesn’t exist, does nothing.
 M.delete_data = function(tree, node, save_tree, opts)
-  if (node.data == nil) then
-    notify('no files associated to this node', vim.log.levels.ERROR)
+  if node.data == nil then
+    notify("no files associated to this node", vim.log.levels.ERROR)
     return
   else
     mind_ui.with_confirmation("Delete file?", function()
@@ -196,8 +241,8 @@ end
 M.open_data_line = function(tree, line, directory, save_tree, opts)
   local node = mind_node.get_node_by_line(tree, line)
 
-  if (node == nil) then
-    notify('cannot open data; no node', vim.log.levels.ERROR)
+  if node == nil then
+    notify("cannot open data; no node", vim.log.levels.ERROR)
     return
   end
 
@@ -217,8 +262,8 @@ end
 M.delete_data_line = function(tree, line, save_tree, opts)
   local node = mind_node.get_node_by_line(tree, line)
 
-  if (node == nil) then
-    notify('cannot delete data; no node', vim.log.levels.ERROR)
+  if node == nil then
+    notify("cannot delete data; no node", vim.log.levels.ERROR)
     return
   end
 
@@ -236,10 +281,12 @@ end
 M.open_data_index = function(tree, directory, save_tree, opts)
   mind_indexing.search_index(
     tree,
-    'Open data / URL',
+    "Open data / URL",
     -- filter function
     function(node)
-      return opts.tree.automatic_data_creation or node.data ~= nil or node.url ~= nil
+      return opts.tree.automatic_data_creation
+        or node.data ~= nil
+        or node.url ~= nil
     end,
     -- sink function
     function(item)
@@ -259,8 +306,11 @@ M.copy_node_link = function(node, reg, opts)
   local link = node.data or node.url
 
   if link ~= nil then
-    notify('link was copied')
-    vim.fn.setreg(reg or '"', string.format(opts.edit.copy_link_format or '%s', link))
+    notify("link was copied")
+    vim.fn.setreg(
+      reg or '"',
+      string.format(opts.edit.copy_link_format or "%s", link)
+    )
   end
 end
 
@@ -281,7 +331,7 @@ end
 M.copy_node_link_index = function(tree, reg, opts)
   mind_indexing.search_index(
     tree,
-    'Get a node link',
+    "Get a node link",
     -- filter function
     function(node)
       return node.data ~= nil or node.url ~= nil
@@ -299,11 +349,11 @@ end
 -- For this to work, the node must not have any data associated with it.
 M.make_url_node = function(tree, node, save_tree, opts)
   if node.data ~= nil then
-    notify('cannot create URL node: data present', vim.log.levels.ERROR)
+    notify("cannot create URL node: data present", vim.log.levels.ERROR)
     return
   end
 
-  mind_ui.with_input('URL: ', 'https://', function(input)
+  mind_ui.with_input("URL: ", "https://", function(input)
     node.url = input
     save_tree()
     mind_ui.rerender(tree, opts)
@@ -325,20 +375,20 @@ end
 
 -- Add a node as child of another node.
 M.create_node = function(tree, grand_parent, parent, node, dir, opts)
-  if (dir == mind_node.MoveDir.INSIDE_START) then
+  if dir == mind_node.MoveDir.INSIDE_START then
     mind_node.insert_node(parent, 1, node)
-  elseif (dir == mind_node.MoveDir.INSIDE_END) then
+  elseif dir == mind_node.MoveDir.INSIDE_END then
     mind_node.insert_node(parent, -1, node)
-  elseif (grand_parent ~= nil) then
+  elseif grand_parent ~= nil then
     local index = mind_node.find_parent_index(grand_parent, parent)
 
-    if (dir == mind_node.MoveDir.ABOVE) then
+    if dir == mind_node.MoveDir.ABOVE then
       mind_node.insert_node(grand_parent, index, node)
-    elseif (dir == mind_node.MoveDir.BELOW) then
+    elseif dir == mind_node.MoveDir.BELOW then
       mind_node.insert_node(grand_parent, index + 1, node)
     end
   else
-    notify('forbidden node creation', vim.log.levels.WARN)
+    notify("forbidden node creation", vim.log.levels.WARN)
     return
   end
 
@@ -349,8 +399,8 @@ end
 M.create_node_line = function(tree, line, name, dir, save_tree, opts)
   local grand_parent, parent = mind_node.get_node_and_parent_by_line(tree, line)
 
-  if (parent == nil) then
-    notify('cannot create node on current line; no node', vim.log.levels.ERROR)
+  if parent == nil then
+    notify("cannot create node on current line; no node", vim.log.levels.ERROR)
     return
   end
 
@@ -363,7 +413,7 @@ end
 -- Ask the user for input and the node in the tree at the given direction.
 M.create_node_cursor = function(tree, dir, save_tree, opts)
   mind_ui.with_cursor(function(line)
-    mind_ui.with_input('Node name: ', nil, function(input)
+    mind_ui.with_input("Node name: ", nil, function(input)
       M.create_node_line(tree, line, input, dir, save_tree, opts)
     end)
   end)
@@ -373,12 +423,12 @@ end
 M.create_node_index = function(tree, dir, save_tree, opts)
   mind_indexing.search_index(
     tree,
-    'Pick a node to create a new node in',
+    "Pick a node to create a new node in",
     -- filter function
     nil,
     -- sink function
     function(item)
-      mind_ui.with_input('Node name: ', nil, function(input)
+      mind_ui.with_input("Node name: ", nil, function(input)
         local node = mind_node.new_node(input)
         M.create_node(tree, item.parent, item.node, node, dir, opts)
         save_tree()
@@ -392,23 +442,26 @@ end
 M.delete_node_line = function(tree, line, save_tree, opts)
   local parent, node = mind_node.get_node_and_parent_by_line(tree, line)
 
-  if (node == nil) then
-    notify('no node to delete', vim.log.levels.ERROR)
+  if node == nil then
+    notify("no node to delete", vim.log.levels.ERROR)
     return
   end
 
-  if (parent == nil) then
-    notify('cannot delete a node without parent', vim.log.levels.ERROR)
+  if parent == nil then
+    notify("cannot delete a node without parent", vim.log.levels.ERROR)
     return
   end
 
   local index = mind_node.find_parent_index(parent, node)
 
-  mind_ui.with_confirmation(string.format("Delete '%s'?", node.contents[1].text), function()
-    mind_node.delete_node(parent, index)
-    mind_ui.rerender(tree, opts)
-    save_tree()
-  end)
+  mind_ui.with_confirmation(
+    string.format("Delete '%s'?", node.contents[1].text),
+    function()
+      mind_node.delete_node(parent, index)
+      mind_ui.rerender(tree, opts)
+      save_tree()
+    end
+  )
 end
 
 -- Delete the node under the cursor.
@@ -420,7 +473,7 @@ end
 
 -- Rename a node.
 M.rename_node = function(tree, node, save_tree, opts)
-  mind_ui.with_input('Rename node: ', node.contents[1].text, function(input)
+  mind_ui.with_input("Rename node: ", node.contents[1].text, function(input)
     node.contents[1].text = input
     M.unselect_node()
     mind_ui.rerender(tree, opts)
@@ -443,8 +496,8 @@ end
 
 -- Change the icon of a node.
 M.change_icon = function(tree, node, save_tree, opts)
-  mind_ui.with_input('Change icon: ', node.icon, function(input)
-    if input == ' ' then
+  mind_ui.with_input("Change icon: ", node.icon, function(input)
+    if input == " " then
       input = nil
     end
 
@@ -469,25 +522,21 @@ end
 
 -- Change the icon of a node by selecting through the list of preset icons.
 M.change_icon_menu = function(tree, node, save_tree, opts)
-  local prompt = string.format('Pick an icon for %s', node.contents[1].text)
+  local prompt = string.format("Pick an icon for %s", node.contents[1].text)
   local format_item = function(item)
-    return string.format('%s: %s', item[1], item[2])
+    return string.format("%s: %s", item[1], item[2])
   end
 
-  vim.ui.select(
-    opts.ui.icon_preset,
-    {
-      prompt = prompt,
-      format_item = format_item
-    },
-    function(item)
-      if item ~= nil then
-        node.icon = item[1]
-        save_tree()
-        mind_ui.rerender(tree, opts)
-      end
+  vim.ui.select(opts.ui.icon_preset, {
+    prompt = prompt,
+    format_item = format_item,
+  }, function(item)
+    if item ~= nil then
+      node.icon = item[1]
+      save_tree()
+      mind_ui.rerender(tree, opts)
     end
-  )
+  end)
 end
 
 -- Change the icon of the node at a given line through the list of preset icons.
@@ -523,10 +572,10 @@ end
 
 -- Select a node by path.
 M.select_node_path = function(tree, opts)
-  mind_ui.with_input('Path: /', nil, function(input)
+  mind_ui.with_input("Path: /", nil, function(input)
     local parent, node = mind_node.get_node_by_path(
       tree,
-      '/' .. input,
+      "/" .. input,
       opts.tree.automatic_creation
     )
 
@@ -538,7 +587,7 @@ end
 
 -- Unselect any selected node in the tree.
 M.unselect_node = function()
-  if (M.selected ~= nil) then
+  if M.selected ~= nil then
     M.selected.node.is_selected = nil
     M.selected = nil
 
@@ -552,9 +601,9 @@ end
 -- something, you need to toggle the currently selected node.
 M.toggle_select_node_cursor = function(tree, opts)
   mind_ui.with_cursor(function(line)
-    if (M.selected ~= nil) then
+    if M.selected ~= nil then
       local node = mind_node.get_node_by_line(tree, line)
-      if (node == M.selected.node) then
+      if node == M.selected.node then
         M.unselect_node()
         mind_ui.rerender(tree, opts)
       else
@@ -577,63 +626,63 @@ M.move_node = function(
   dir,
   opts
 )
-  if (source_node == nil) then
-    notify('cannot move; no source node', vim.log.levels.WARN)
+  if source_node == nil then
+    notify("cannot move; no source node", vim.log.levels.WARN)
     return
   end
 
-  if (target_node == nil) then
-    notify('cannot move; no target node', vim.log.levels.WARN)
+  if target_node == nil then
+    notify("cannot move; no target node", vim.log.levels.WARN)
     return
   end
 
   -- if we move in the same tree, we can optimize
-  if (source_parent == target_parent) then
+  if source_parent == target_parent then
     -- compute the index of the nodes to move
     local source_i
     local target_i
     for k, child in ipairs(source_parent.children) do
-      if (child == target_node) then
+      if child == target_node then
         target_i = k
-      elseif (child == source_node) then
+      elseif child == source_node then
         source_i = k
       end
 
-      if (target_i ~= nil and source_i ~= nil) then
+      if target_i ~= nil and source_i ~= nil then
         break
       end
     end
 
-    if (target_i == nil or source_i == nil) then
+    if target_i == nil or source_i == nil then
       -- trying to move inside itsefl; abort
       M.unselect_node()
       mind_ui.rerender(tree, opts)
       return
     end
 
-    if (target_i == source_i) then
+    if target_i == source_i then
       -- same node; aborting
-      notify('not moving; source and target are the same node')
+      notify("not moving; source and target are the same node")
       M.unselect_node()
       mind_ui.rerender(tree, opts)
       return
     end
 
-    if (dir == mind_node.MoveDir.BELOW) then
+    if dir == mind_node.MoveDir.BELOW then
       mind_node.move_source_target_same_tree(
         source_parent,
         source_i,
         target_i + 1
       )
-    elseif (dir == mind_node.MoveDir.ABOVE) then
+    elseif dir == mind_node.MoveDir.ABOVE then
       mind_node.move_source_target_same_tree(source_parent, source_i, target_i)
     else
       -- we move inside, so first remove the node
       mind_node.delete_node(source_parent, source_i)
 
-      if (dir == mind_node.MoveDir.INSIDE_START) then
+      if dir == mind_node.MoveDir.INSIDE_START then
         mind_node.insert_node(target_node, 1, source_node)
-      elseif (dir == mind_node.MoveDir.INSIDE_END) then
+      elseif dir == mind_node.MoveDir.INSIDE_END then
         mind_node.insert_node(target_node, -1, source_node)
       end
     end
@@ -645,13 +694,13 @@ M.move_node = function(
     -- then insert the previously deleted node in the new tree
     local target_i = mind_node.find_parent_index(target_parent, target_node)
 
-    if (dir == mind_node.MoveDir.BELOW) then
+    if dir == mind_node.MoveDir.BELOW then
       mind_node.insert_node(target_parent, target_i + 1, source_node)
-    elseif (dir == mind_node.MoveDir.ABOVE) then
+    elseif dir == mind_node.MoveDir.ABOVE then
       mind_node.insert_node(target_parent, target_i, source_node)
-    elseif (dir == mind_node.MoveDir.INSIDE_START) then
+    elseif dir == mind_node.MoveDir.INSIDE_START then
       mind_node.insert_node(target_node, 1, source_node)
-    elseif (dir == mind_node.MoveDir.INSIDE_END) then
+    elseif dir == mind_node.MoveDir.INSIDE_END then
       mind_node.insert_node(target_node, -1, source_node)
     end
   end
@@ -662,8 +711,8 @@ end
 
 -- Move a selected node into a node at the given line.
 M.move_node_selected_line = function(tree, line, dir, save_tree, opts)
-  if (M.selected == nil) then
-    notify('cannot move; no selected node', vim.log.levels.ERROR)
+  if M.selected == nil then
+    notify("cannot move; no selected node", vim.log.levels.ERROR)
     M.unselect_node()
     mind_ui.rerender(tree, opts)
     return
@@ -671,22 +720,14 @@ M.move_node_selected_line = function(tree, line, dir, save_tree, opts)
 
   local parent, node = mind_node.get_node_and_parent_by_line(tree, line)
 
-  if (parent == nil) then
-    notify('cannot move root', vim.log.levels.ERROR)
+  if parent == nil then
+    notify("cannot move root", vim.log.levels.ERROR)
     M.unselect_node()
     mind_ui.rerender(tree, opts)
     return
   end
 
-  M.move_node(
-    tree,
-    M.selected.parent,
-    M.selected.node,
-    parent,
-    node,
-    dir,
-    opts
-  )
+  M.move_node(tree, M.selected.parent, M.selected.node, parent, node, dir, opts)
 
   save_tree()
 end
@@ -706,7 +747,7 @@ M.toggle_node = function(tree, node, save_tree, opts)
 end
 
 -- Toggle (expand / collapse) a node at a given line.
-M.toggle_node_line = function(tree, line, save_tree,opts)
+M.toggle_node_line = function(tree, line, save_tree, opts)
   local node = mind_node.get_node_by_line(tree, line)
   M.toggle_node(tree, node, save_tree, opts)
 end
@@ -736,16 +777,13 @@ M.open_tree = function(get_tree, data_dir, save_tree, opts)
 
   -- ensure that we close the tree if the window gets closed
   local id
-  id = vim.api.nvim_create_autocmd(
-    { 'WinClosed' },
-    {
-      buffer = bufnr,
-      callback = function()
-        vim.api.nvim_del_autocmd(id)
-        M.close()
-      end
-    }
-  )
+  id = vim.api.nvim_create_autocmd({ "WinClosed" }, {
+    buffer = bufnr,
+    callback = function()
+      vim.api.nvim_del_autocmd(id)
+      M.close()
+    end,
+  })
 
   -- tree
   mind_ui.render(get_tree(), bufnr, opts)
@@ -773,10 +811,10 @@ end
 -- name is a string.
 M.precompute_commands = function()
   for key, c in pairs(mind_keymap.keymaps.normal) do
-    if type(c) == 'string' then
+    if type(c) == "string" then
       local cmd = M.commands[mind_keymap.keymaps.normal[key]]
 
-      if (cmd ~= nil) then
+      if cmd ~= nil then
         mind_keymap.keymaps.normal[key] = cmd
       end
     elseif c == false then
@@ -786,10 +824,10 @@ M.precompute_commands = function()
   end
 
   for key, c in pairs(mind_keymap.keymaps.selection) do
-    if type(c) == 'string' then
+    if type(c) == "string" then
       local cmd = M.commands[mind_keymap.keymaps.selection[key]]
 
-      if (cmd ~= nil) then
+      if cmd ~= nil then
         mind_keymap.keymaps.selection[key] = cmd
       end
     elseif c == false then
diff --git a/lua/mind/data.lua b/lua/mind/data.lua
index b6bcb36..2a42b78 100644
--- a/lua/mind/data.lua
+++ b/lua/mind/data.lua
@@ -2,8 +2,8 @@
 
 local M = {}
 
-local notify = require'mind.notify'.notify
-local path = require'plenary.path'
+local notify = require("mind.notify").notify
+local path = require("plenary.path")
 
 -- Create a new random file in a given directory.
 --
@@ -16,20 +16,20 @@ M.new_data_file = function(dir, name, extension, content, should_expand)
   end
 
   -- filter the name
-  name = name:gsub('[^%w-]', ' ') -- remove anything that is not a word or a dash
-  name = name:gsub('%s+', '-') -- replace consecutive spaces with a single one
-  name = name:gsub('-+', '-') -- replace consecutive dashes with a single one
-  name = name:gsub('^-', '') -- remove leading dash
-  name = name:gsub('-$', '') -- remove trailing dash
+  name = name:gsub("[^%w-]", " ") -- remove anything that is not a word or a dash
+  name = name:gsub("%s+", "-") -- replace consecutive spaces with a single one
+  name = name:gsub("-+", "-") -- replace consecutive dashes with a single one
+  name = name:gsub("^-", "") -- remove leading dash
+  name = name:gsub("-$", "") -- remove trailing dash
 
-  local filename = vim.fn.strftime('%Y%m%d%H%M%S-') .. name .. extension
+  local filename = vim.fn.strftime("%Y%m%d%H%M%S-") .. name .. extension
   local p = path:new(dir, filename)
   local file_path = (should_expand and p:expand()) or tostring(p)
 
-  local file = io.open(file_path, 'w')
+  local file = io.open(file_path, "w")
 
-  if (file == nil) then
-    notify('cannot open data file: ' .. file_path)
+  if file == nil then
+    notify("cannot open data file: " .. file_path)
     return nil
   end
 
@@ -44,5 +44,4 @@ M.delete_data_file = function(file_path)
   os.remove(file_path)
 end
 
-
 return M
diff --git a/lua/mind/defaults.lua b/lua/mind/defaults.lua
index c22f991..8da207d 100644
--- a/lua/mind/defaults.lua
+++ b/lua/mind/defaults.lua
@@ -3,11 +3,11 @@
 -- URL opener depends on the platform.
 local sysname = vim.loop.os_uname().sysname
 local url_open
-if sysname == 'Linux' then
-  url_open = 'xdg-open'
-elseif sysname == 'Darwin' then
-  url_open = 'open'
-elseif sysname == 'Windows' then
+if sysname == "Linux" then
+  url_open = "xdg-open"
+elseif sysname == "Darwin" then
+  url_open = "open"
+elseif sysname == "Windows" then
   url_open = 'start ""'
 end
 
@@ -15,22 +15,22 @@ return {
   -- persistence, both for the tree state and data files
   persistence = {
     -- path where the global mind tree is stored
-    state_path = '~/.local/share/mind.nvim/mind.json',
+    state_path = "~/.local/share/mind.nvim/mind.json",
 
     -- directory where to create global data files
-    data_dir = '~/.local/share/mind.nvim/data',
+    data_dir = "~/.local/share/mind.nvim/data",
   },
 
   -- edit options
   edit = {
     -- file extension to use when creating a data file
-    data_extension = '.md',
+    data_extension = ".md",
 
     -- default header to put in newly created data files
-    data_header = '# %s',
+    data_header = "# %s",
 
     -- format string for copied links
-    copy_link_format = '[](%s)'
+    copy_link_format = "[](%s)",
   },
 
   -- tree options
@@ -51,119 +51,124 @@ return {
     -- default width of the tree view window
     width = 30,
 
+    -- split to open window in
+    position = "left",
+
     -- should mind window be closed when a file is opened
     close_on_file_open = false,
 
     -- marker used for empty indentation
-    empty_indent_marker = '│',
+    empty_indent_marker = "│",
 
     -- marker used for node indentation
-    node_indent_marker = '└',
+    node_indent_marker = "└",
 
     -- marker used to identify the root of the tree (left to its name)
-    root_marker = ' ',
+    root_marker = " ",
 
     -- marker used to identify a local root (right to its name)
-    local_marker = 'local',
+    local_marker = "local",
 
     -- marker used to show that a node has an associated data file
-    data_marker = ' ',
+    data_marker = " ",
 
     -- marker used to show that a node has an URL
-    url_marker = ' ',
+    url_marker = " ",
 
     -- marker used to show that a node is currently selected
-    select_marker = '',
+    select_marker = "",
 
     -- highlight options
     highlight = {
       -- highlight used on closed marks
-      closed_marker = 'LineNr',
+      closed_marker = "LineNr",
 
       -- highlight used on open marks
-      open_marker = 'LineNr',
+      open_marker = "LineNr",
 
       -- highlight used on the name of the root node
-      node_root = 'Function',
+      node_root = "Function",
 
       -- highlight used on regular nodes with no children
-      node_leaf = 'String',
+      node_leaf = "String",
 
       -- highlight used on regular nodes with children
-      node_parent = 'Title',
+      node_parent = "Title",
 
       -- highlight used on the local marker
-      local_marker = 'Comment',
+      local_marker = "Comment",
 
       -- highlight used on the data marker
-      data_marker = 'Comment',
+      data_marker = "Comment",
 
       -- highlight used on the url marker
-      url_marker = 'Comment',
+      url_marker = "Comment",
 
       -- highlight used on empty nodes (i.e. no children and no data)
-      modifier_empty = 'Comment',
+      modifier_empty = "Comment",
 
       -- highlight used on the selection marker
-      select_marker = 'Error',
+      select_marker = "Error",
     },
 
     -- preset of icons
     icon_preset = {
-      { ' ', 'Sub-project' },
-      { ' ', 'Journal, newspaper, weekly and daily news' },
-      { ' ', 'For when you have an idea' },
-      { ' ', 'Note taking?' },
-      { '陼', 'Task management' },
-      { ' ', 'Uncheck, empty square or backlog' },
-      { ' ', 'Full square or on-going' },
-      { ' ', 'Check or done' },
-      { ' ', 'Trash bin, deleted, cancelled, etc.' },
-      { ' ', 'GitHub' },
-      { ' ', 'Monitoring' },
-      { ' ', 'Internet, Earth, everyone!' },
-      { ' ', 'Frozen, on-hold' },
-    }
+      { " ", "Sub-project" },
+      { " ", "Journal, newspaper, weekly and daily news" },
+      { " ", "For when you have an idea" },
+      { " ", "Note taking?" },
+      { "陼", "Task management" },
+      { " ", "Uncheck, empty square or backlog" },
+      { " ", "Full square or on-going" },
+      { " ", "Check or done" },
+      { " ", "Trash bin, deleted, cancelled, etc." },
+      { " ", "GitHub" },
+      { " ", "Monitoring" },
+      { " ", "Internet, Earth, everyone!" },
+      { " ", "Frozen, on-hold" },
+      { " ", "Data, knowledge" },
+      { " ", "Neovim" },
+    },
   },
 
   -- default keymaps; see 'mind.commands' for a list of commands that can be mapped to keys here
   keymaps = {
     -- keybindings when navigating the tree normally
     normal = {
-      ['<cr>'] = 'open_data',
-      ['<s-cr>'] = 'open_data_index',
-      ['<tab>'] = 'toggle_node',
-      ['<s-tab>'] = 'toggle_parent',
-      ['/'] = 'select_path',
-      ['$'] = 'change_icon_menu',
-      c = 'add_inside_end_index',
-      I = 'add_inside_start',
-      i = 'add_inside_end',
-      l = 'copy_node_link',
-      L = 'copy_node_link_index',
-      d = 'delete',
-      D = 'delete_file',
-      O = 'add_above',
-      o = 'add_below',
-      q = 'quit',
-      r = 'rename',
-      R = 'change_icon',
-      u = 'make_url',
-      x = 'select',
+      ["<cr>"] = "open_data",
+      ["<s-cr>"] = "open_data_index",
+      ["<tab>"] = "toggle_node",
+      ["<s-tab>"] = "toggle_parent",
+      ["/"] = "select_path",
+      ["$"] = "change_icon_menu",
+      c = "add_inside_end_index",
+      I = "add_inside_start",
+      i = "add_inside_end",
+      l = "copy_node_link",
+      L = "copy_node_link_index",
+      d = "delete",
+      D = "delete_file",
+      O = "add_above",
+      o = "add_below",
+      q = "quit",
+      r = "rename",
+      R = "change_icon",
+      u = "make_url",
+      x = "select",
     },
 
     -- keybindings when a node is selected
     selection = {
-      ['<cr>'] = 'open_data',
-      ['<tab>'] = 'toggle_node',
-      ['<s-tab>'] = 'toggle_parent',
-      ['/'] = 'select_path',
-      I = 'move_inside_start',
-      i = 'move_inside_end',
-      O = 'move_above',
-      o = 'move_below',
-      q = 'quit',
-      x = 'select',
+      ["<cr>"] = "open_data",
+      ["<tab>"] = "toggle_node",
+      ["<s-tab>"] = "toggle_parent",
+      ["/"] = "select_path",
+      I = "move_inside_start",
+      i = "move_inside_end",
+      O = "move_above",
+      o = "move_below",
+      q = "quit",
+      x = "select",
     },
-  }
+  },
 }
diff --git a/lua/mind/highlight.lua b/lua/mind/highlight.lua
index 8c2eeed..640d167 100644
--- a/lua/mind/highlight.lua
+++ b/lua/mind/highlight.lua
@@ -4,34 +4,74 @@ local M = {}
 
 M.create_highlight_groups = function(opts)
   -- highlight used on closed marks
-  vim.api.nvim_set_hl(0, 'MindClosedMarker', { default = true, link = opts.ui.highlight.closed_marker })
+  vim.api.nvim_set_hl(
+    0,
+    "MindClosedMarker",
+    { default = true, link = opts.ui.highlight.closed_marker }
+  )
 
   -- highlight used on open marks
-  vim.api.nvim_set_hl(0, 'MindOpenMarker', { default = true, link = opts.ui.highlight.open_marker })
+  vim.api.nvim_set_hl(
+    0,
+    "MindOpenMarker",
+    { default = true, link = opts.ui.highlight.open_marker }
+  )
 
   -- highlight used on the name of the root node
-  vim.api.nvim_set_hl(0, 'MindNodeRoot', { default = true, link = opts.ui.highlight.node_root })
+  vim.api.nvim_set_hl(
+    0,
+    "MindNodeRoot",
+    { default = true, link = opts.ui.highlight.node_root }
+  )
 
   -- highlight used on regular nodes with no children
-  vim.api.nvim_set_hl(0, 'MindNodeLeaf', { default = true, link = opts.ui.highlight.node_leaf })
+  vim.api.nvim_set_hl(
+    0,
+    "MindNodeLeaf",
+    { default = true, link = opts.ui.highlight.node_leaf }
+  )
 
   -- highlight used on regular nodes with children
-  vim.api.nvim_set_hl(0, 'MindNodeParent', { default = true, link = opts.ui.highlight.node_parent })
+  vim.api.nvim_set_hl(
+    0,
+    "MindNodeParent",
+    { default = true, link = opts.ui.highlight.node_parent }
+  )
 
   -- highlight used on the local marker
-  vim.api.nvim_set_hl(0, 'MindLocalMarker', { default = true, link = opts.ui.highlight.local_marker })
+  vim.api.nvim_set_hl(
+    0,
+    "MindLocalMarker",
+    { default = true, link = opts.ui.highlight.local_marker }
+  )
 
   -- highlight used on the data marker
-  vim.api.nvim_set_hl(0, 'MindDataMarker', { default = true, link = opts.ui.highlight.data_marker })
+  vim.api.nvim_set_hl(
+    0,
+    "MindDataMarker",
+    { default = true, link = opts.ui.highlight.data_marker }
+  )
 
   -- highlight used on the URL marker
-  vim.api.nvim_set_hl(0, 'MindURLMarker', { default = true, link = opts.ui.highlight.url_marker })
+  vim.api.nvim_set_hl(
+    0,
+    "MindURLMarker",
+    { default = true, link = opts.ui.highlight.url_marker }
+  )
 
   -- highlight used on empty nodes (i.e. no children and no data)
-  vim.api.nvim_set_hl(0, 'MindModifierEmpty', { default = true, link = opts.ui.highlight.modifier_empty })
+  vim.api.nvim_set_hl(
+    0,
+    "MindModifierEmpty",
+    { default = true, link = opts.ui.highlight.modifier_empty }
+  )
 
   -- highlight used on the selection marker
-  vim.api.nvim_set_hl(0, 'MindSelectMarker', { default = true, link = opts.ui.highlight.select_marker })
+  vim.api.nvim_set_hl(
+    0,
+    "MindSelectMarker",
+    { default = true, link = opts.ui.highlight.select_marker }
+  )
 end
 
 return M
diff --git a/lua/mind/indexing.lua b/lua/mind/indexing.lua
index 10864f9..900c57a 100644
--- a/lua/mind/indexing.lua
+++ b/lua/mind/indexing.lua
@@ -9,14 +9,18 @@ M.index = {}
 
 -- Index a node and its children
 M.index_node = function(parent_path, parent, node, filter, opts)
-  local path = string.format('%s%s', parent_path, node.type and '/' or node.contents[1].text)
+  local path = string.format(
+    "%s%s",
+    parent_path,
+    node.type and "/" or node.contents[1].text
+  )
 
   if filter == nil or filter(node) then
     M.index[#M.index + 1] = { path = path, parent = parent, node = node }
   end
 
   if node.children ~= nil then
-    local child_path = node.type and path or path .. '/'
+    local child_path = node.type and path or path .. "/"
     for _, child in ipairs(node.children) do
       M.index_node(child_path, node, child, filter, opts)
     end
@@ -26,13 +30,13 @@ end
 -- Index a whole tree.
 M.index_tree = function(tree, filter, opts)
   M.index = {}
-  M.index_node('', nil, tree, filter, opts)
+  M.index_node("", nil, tree, filter, opts)
 end
 
 -- Search through the index.
 M.search_index = function(tree, prompt, filter, f, opts)
   local format_item = function(item)
-    local prefix = ''
+    local prefix = ""
 
     if item.node.data ~= nil then
       prefix = opts.ui.data_marker
@@ -45,11 +49,15 @@ M.search_index = function(tree, prompt, filter, f, opts)
 
   M.index_tree(tree, filter, opts)
 
-  vim.ui.select(M.index, { prompt = prompt, format_item = format_item }, function(item)
-    if item ~= nil then
-      f(item)
+  vim.ui.select(
+    M.index,
+    { prompt = prompt, format_item = format_item },
+    function(item)
+      if item ~= nil then
+        f(item)
+      end
     end
-  end)
+  )
 end
 
 return M
diff --git a/lua/mind/init.lua b/lua/mind/init.lua
index afea03b..190e903 100644
--- a/lua/mind/init.lua
+++ b/lua/mind/init.lua
@@ -76,54 +76,50 @@ end
 
 -- Open the main tree.
 M.open_main = function()
-  M.wrap_main_tree_fn(
-    function(args)
-      mind_commands.open_tree(
-        args.get_tree,
-        args.opts.persistence.data_dir,
-        function() mind_state.save_main_state(args.opts) end,
-        args.opts
-      )
-    end,
-    M.opts
-  )
+  M.wrap_main_tree_fn(function(args)
+    mind_commands.open_tree(
+      args.get_tree,
+      args.opts.persistence.data_dir,
+      function()
+        mind_state.save_main_state(args.opts)
+      end,
+      args.opts
+    )
+  end, M.opts)
 end
 
 -- Open a project tree.
 --
 -- If `use_global` is set to `true`, will use the global persistence location.
 M.open_project = function(use_global)
-  M.wrap_project_tree_fn(
-    function(args)
-      mind_commands.open_tree(
-        args.get_tree,
-        args.data_dir,
-        use_global
-          and function() mind_state.save_main_state(args.opts) end
-          or function() mind_state.save_local_state() end,
-        args.opts
-      )
-    end,
-    use_global,
-    M.opts
-  )
+  M.wrap_project_tree_fn(function(args)
+    mind_commands.open_tree(
+      args.get_tree,
+      args.data_dir,
+      use_global and function()
+          mind_state.save_main_state(args.opts)
+        end or function()
+          mind_state.save_local_state()
+        end,
+      args.opts
+    )
+  end, use_global, M.opts)
 end
 
 -- Open a smart project tree.
 M.open_smart_project = function()
-  M.wrap_smart_project_tree_fn(
-    function(args, use_global)
-      mind_commands.open_tree(
-        args.get_tree,
-        args.data_dir,
-        use_global
-          and function() mind_state.save_main_state(args.opts) end
-          or function() mind_state.save_local_state() end,
-        args.opts
-      )
-    end,
-    M.opts
-  )
+  M.wrap_smart_project_tree_fn(function(args, use_global)
+    mind_commands.open_tree(
+      args.get_tree,
+      args.data_dir,
+      use_global and function()
+          mind_state.save_main_state(args.opts)
+        end or function()
+          mind_state.save_local_state()
+        end,
+      args.opts
+    )
+  end, M.opts)
 end
 
 -- Load state.
@@ -133,7 +129,7 @@ end
 
 -- Wrap a function call expecting the main tree.
 M.wrap_main_tree_fn = function(f, opts)
-  opts = vim.tbl_deep_extend('force', M.opts, opts or {})
+  opts = vim.tbl_deep_extend("force", M.opts, opts or {})
 
   -- load the main tree
   mind_state.load_main_state(opts)
@@ -141,7 +137,9 @@ M.wrap_main_tree_fn = function(f, opts)
   local args = {
     get_tree = mind_state.get_main_tree,
     data_dir = opts.persistence.data_dir,
-    save_tree = function() mind_state.save_main_state(opts) end,
+    save_tree = function()
+      mind_state.save_main_state(opts)
+    end,
     opts = opts,
   }
 
@@ -152,13 +150,13 @@ end
 --
 -- If the project tree doesn’t exist, it is automatically created.
 M.wrap_project_tree_fn = function(f, use_global, opts)
-  opts = vim.tbl_deep_extend('force', M.opts, opts or {})
+  opts = vim.tbl_deep_extend("force", M.opts, opts or {})
 
   local cwd = vim.fn.getcwd()
   if use_global then
     mind_state.load_main_state(opts)
 
-    if mind_state.state.projects[cwd]== nil then
+    if mind_state.state.projects[cwd] == nil then
       mind_state.new_global_project_tree(cwd, opts)
     end
   else
@@ -170,15 +168,21 @@ M.wrap_project_tree_fn = function(f, use_global, opts)
     end
   end
 
-  local save_tree =
-    use_global and function() mind_state.save_main_state(opts) end
-    or function() mind_state.save_local_state() end
+  local save_tree = use_global
+      and function()
+        mind_state.save_main_state(opts)
+      end
+    or function()
+      mind_state.save_local_state()
+    end
 
   local args = {
-    get_tree = function() return mind_state.get_project_tree(use_global and cwd or nil) end,
+    get_tree = function()
+      return mind_state.get_project_tree(use_global and cwd or nil)
+    end,
     data_dir = mind_state.get_project_data_dir(use_global, opts),
     save_tree = save_tree,
-    opts = opts
+    opts = opts,
   }
 
   f(args)
@@ -188,19 +192,23 @@ end
 --
 -- If a local tree exists, wrap the local tree. Otherwise, wrap a global tree.
 M.wrap_smart_project_tree_fn = function(f, opts)
-  opts = vim.tbl_deep_extend('force', M.opts, opts or {})
+  opts = vim.tbl_deep_extend("force", M.opts, opts or {})
 
   local cwd = vim.fn.getcwd()
-  local p = path:new(cwd, '.mind')
+  local p = path:new(cwd, ".mind")
 
   if p:exists() and p:is_dir() then
     -- load the local state
     mind_state.load_local_state()
 
     local args = {
-      get_tree = function() return mind_state.get_project_tree() end,
+      get_tree = function()
+        return mind_state.get_project_tree()
+      end,
       data_dir = mind_state.get_project_data_dir(false, opts),
-      save_tree = function() mind_state.save_local_state() end,
+      save_tree = function()
+        mind_state.save_local_state()
+      end,
       opts = opts,
     }
 
@@ -214,47 +222,66 @@ M.wrap_smart_project_tree_fn = function(f, opts)
     if tree ~= nil then
       -- a global project tree exists, use that
       local args = {
-        get_tree = function() return mind_state.get_project_tree(cwd) end,
+        get_tree = function()
+          return mind_state.get_project_tree(cwd)
+        end,
         data_dir = mind_state.get_project_data_dir(true, opts),
-        save_tree = function() mind_state.save_main_state(opts) end,
+        save_tree = function()
+          mind_state.save_main_state(opts)
+        end,
         opts = opts,
       }
 
       f(args, true)
     else
       -- prompt the user whether they want a global or local tree
-      mind_ui.with_input('What kind of project tree? (local/global) ', 'local', function(input)
-        local get_tree
-        local save_tree
-        local use_global
-
-        if input == 'local' then
-          mind_state.new_local_tree(cwd, opts)
-          get_tree = function() return mind_state.get_project_tree() end
-          save_tree = function() mind_state.save_local_state() end
-          use_global = false
-        elseif input == 'global' then
-          mind_state.new_global_project_tree(cwd, opts)
-          get_tree = function() return mind_state.get_project_tree(cwd) end
-          save_tree = function() mind_state.save_main_state(opts) end
-          use_global = true
-        end
-
-        if get_tree == nil then
-          notify('unrecognized project tree type, aborting', vim.log.levels.WARN)
-          return
+      mind_ui.with_input(
+        "What kind of project tree? (local/global) ",
+        "local",
+        function(input)
+          local get_tree
+          local save_tree
+          local use_global
+
+          if input == "local" then
+            mind_state.new_local_tree(cwd, opts)
+            get_tree = function()
+              return mind_state.get_project_tree()
+            end
+            save_tree = function()
+              mind_state.save_local_state()
+            end
+            use_global = false
+          elseif input == "global" then
+            mind_state.new_global_project_tree(cwd, opts)
+            get_tree = function()
+              return mind_state.get_project_tree(cwd)
+            end
+            save_tree = function()
+              mind_state.save_main_state(opts)
+            end
+            use_global = true
+          end
+
+          if get_tree == nil then
+            notify(
+              "unrecognized project tree type, aborting",
+              vim.log.levels.WARN
+            )
+            return
+          end
+
+          local args = {
+            get_tree = get_tree,
+            data_dir = mind_state.get_project_data_dir(use_global, opts),
+            save_tree = save_tree,
+            opts = opts,
+          }
+
+          f(args, true)
+          save_tree()
         end
-
-        local args = {
-          get_tree = get_tree,
-          data_dir = mind_state.get_project_data_dir(use_global, opts),
-          save_tree = save_tree,
-          opts = opts,
-        }
-
-        f(args, true)
-        save_tree()
-      end)
+      )
     end
   end
 end
diff --git a/lua/mind/keymap.lua b/lua/mind/keymap.lua
index db7f4a3..f52ad14 100644
--- a/lua/mind/keymap.lua
+++ b/lua/mind/keymap.lua
@@ -2,7 +2,7 @@
 
 local M = {}
 
-local notify = require'mind.notify'.notify
+local notify = require("mind.notify").notify
 
 -- Selector for keymap.
 --
@@ -10,8 +10,8 @@ local notify = require'mind.notify'.notify
 -- currently active keymap. The keymap contains user-defined keybindings that will then be resolved when the user
 -- presses their defined keys.
 M.KeymapSelector = {
-  NORMAL = 'normal',
-  SELECTION = 'selection',
+  NORMAL = "normal",
+  SELECTION = "selection",
 }
 
 -- Keymaps.
@@ -64,22 +64,22 @@ M.insert_keymaps = function(bufnr, get_tree, data_dir, save_tree, opts)
     get_tree = get_tree,
     data_dir = data_dir,
     save_tree = save_tree,
-    opts = opts
+    opts = opts,
   }
 
   for key, _ in pairs(keyset) do
-    vim.keymap.set('n', key, function()
+    vim.keymap.set("n", key, function()
       local keymap = M.get_keymap()
 
-      if (keymap == nil) then
-        notify('no active keymap', vim.log.levels.WARN)
+      if keymap == nil then
+        notify("no active keymap", vim.log.levels.WARN)
         return
       end
 
       local cmd = keymap[key]
 
-      if (cmd == nil) then
-        notify('no command bound to ' .. tostring(key), vim.log.levels.WARN)
+      if cmd == nil then
+        notify("no command bound to " .. tostring(key), vim.log.levels.WARN)
         return
       end
 
diff --git a/lua/mind/node.lua b/lua/mind/node.lua
index d45840f..0e5158f 100644
--- a/lua/mind/node.lua
+++ b/lua/mind/node.lua
@@ -1,6 +1,6 @@
 -- Node and trees operations.
 
-local notify = require'mind.notify'.notify
+local notify = require("mind.notify").notify
 
 local M = {}
 
@@ -32,10 +32,10 @@ M.MoveDir = {
 M.new_node = function(name, children)
   return {
     contents = {
-      { text = name }
+      { text = name },
     },
     is_expanded = false,
-    children = children
+    children = children,
   }
 end
 
@@ -44,18 +44,18 @@ end
 -- `i` is rank of the node we want to get. If i is 0, then parent and node are returned as result. If not, this function
 -- will recurse into node.children (if any) and if node.is_expanded is true.
 local function get_dfs(parent, node, i)
-  if (i == 0) then
+  if i == 0 then
     return parent, node, i
   end
 
   i = i - 1
 
-  if (node.children ~= nil and node.is_expanded) then
+  if node.children ~= nil and node.is_expanded then
     for _, child in ipairs(node.children) do
       local p, n
       p, n, i = get_dfs(node, child, i)
 
-      if (n ~= nil) then
+      if n ~= nil then
         return p, n, i
       end
     end
@@ -86,13 +86,13 @@ end
 --
 -- The function stops when it arrives at the end of paths, that is, when i == #paths + 1.
 local function get_node_by_path_rec(parent, tree, paths, i, create)
-  if (i == #paths + 1) then
+  if i == #paths + 1 then
     return parent, tree
   end
 
   local segment = paths[i]
 
-  if (tree.children == nil) then
+  if tree.children == nil then
     if create then
       tree.children = { M.new_node(segment) }
     else
@@ -103,7 +103,7 @@ local function get_node_by_path_rec(parent, tree, paths, i, create)
 
   -- look for the child which name is the same as paths[i]
   for _, child in ipairs(tree.children) do
-    if (child.contents[1].text == segment) then
+    if child.contents[1].text == segment then
       return get_node_by_path_rec(tree, child, paths, i + 1, create)
     end
   end
@@ -122,14 +122,14 @@ end
 --
 -- If `create` is set to `true`, nodes are created automatically if they don’t exist.
 M.get_node_by_path = function(tree, path, create)
-  if (path == '/') then
+  if path == "/" then
     return nil, tree
   end
 
-  local split_path = vim.split(path, '/')
+  local split_path = vim.split(path, "/")
 
-  if (split_path[1] ~= '') then
-    notify('path must start with a leading slash (/)', vim.log.levels.WARN)
+  if split_path[1] ~= "" then
+    notify("path must start with a leading slash (/)", vim.log.levels.WARN)
     return
   end
 
@@ -163,8 +163,8 @@ end
 --
 -- If i is negative, it starts after the end.
 M.delete_node = function(tree, i)
-  if (tree.children == nil) then
-    notify('cannot delete node; no children', vim.log.levels.ERROR)
+  if tree.children == nil then
+    notify("cannot delete node; no children", vim.log.levels.ERROR)
     return
   end
 
@@ -176,7 +176,7 @@ M.delete_node = function(tree, i)
     tree.children[k] = tree.children[k + 1]
   end
 
-  if (#tree.children == 0) then
+  if #tree.children == 0 then
     tree.children = nil
   end
 end
@@ -184,7 +184,7 @@ end
 -- Find the parent index of a node in its parent’s children.
 M.find_parent_index = function(tree, node)
   for i, child in ipairs(tree.children) do
-    if (child == node) then
+    if child == node then
       return i
     end
   end
@@ -193,11 +193,11 @@ end
 -- Move a source node at a target node in the same tree.
 M.move_source_target_same_tree = function(tree, src, tgt)
   -- do nothing if src == tgt
-  if (src == tgt) then
+  if src == tgt then
     return
   end
 
-  if (tgt < src) then
+  if tgt < src then
     -- if we want to move src to tgt with target before source
     local prev = tree.children[src]
 
diff --git a/lua/mind/notify.lua b/lua/mind/notify.lua
index d5b205e..47f0cac 100644
--- a/lua/mind/notify.lua
+++ b/lua/mind/notify.lua
@@ -3,7 +3,7 @@
 local M = {}
 
 M.notify = function(msg, lvl)
-  vim.notify(msg, lvl, { title = 'Mind', icon = '' })
+  vim.notify(msg, lvl, { title = "Mind", icon = "" })
 end
 
 return M
diff --git a/lua/mind/state.lua b/lua/mind/state.lua
index 9dde603..837790f 100644
--- a/lua/mind/state.lua
+++ b/lua/mind/state.lua
@@ -1,8 +1,8 @@
 local M = {}
 
-local path = require'plenary.path'
-local notify = require'mind.notify'.notify
-local mind_node = require'mind.node'
+local path = require("plenary.path")
+local notify = require("mind.notify").notify
+local mind_node = require("mind.node")
 
 -- Expand opts paths.
 --
@@ -27,12 +27,12 @@ M.get_project_tree = function(cwd)
 end
 
 M.new_global_project_tree = function(cwd, opts)
-  notify('creating a new global project tree')
+  notify("creating a new global project tree")
 
   local tree = {
-    uid = vim.fn.strftime('%Y%m%d%H%M%S'),
+    uid = vim.fn.strftime("%Y%m%d%H%M%S"),
     contents = {
-      { text = cwd:match('^.*/(.+)$') },
+      { text = cwd:match("^.*/(.+)$") },
     },
     type = mind_node.TreeType.ROOT,
     icon = opts.ui.root_marker,
@@ -44,12 +44,12 @@ M.new_global_project_tree = function(cwd, opts)
 end
 
 M.new_local_tree = function(cwd, opts)
-  notify('creating a new local tree')
+  notify("creating a new local tree")
 
   M.local_tree = {
-    uid = vim.fn.strftime('%Y%m%d%H%M%S'),
+    uid = vim.fn.strftime("%Y%m%d%H%M%S"),
     contents = {
-      { text = cwd:match('^.*/(.+)$') },
+      { text = cwd:match("^.*/(.+)$") },
     },
     type = mind_node.TreeType.LOCAL_ROOT,
     icon = opts.ui.root_marker,
@@ -64,9 +64,9 @@ M.load_main_state = function(opts)
   M.state = {
     -- Main tree, used when no specific project is wanted.
     tree = {
-      uid = vim.fn.strftime('%Y%m%d%H%M%S'),
+      uid = vim.fn.strftime("%Y%m%d%H%M%S"),
       contents = {
-        { text = 'Main' },
+        { text = "Main" },
       },
       type = mind_node.TreeType.ROOT,
       icon = opts.ui.root_marker,
@@ -76,33 +76,33 @@ M.load_main_state = function(opts)
     projects = {},
   }
 
-  if (opts.persistence.state_path == nil) then
-    notify('cannot load shit', vim.log.levels.ERROR)
+  if opts.persistence.state_path == nil then
+    notify("cannot load shit", vim.log.levels.ERROR)
     return
   end
 
-  local file = io.open(opts.persistence.state_path, 'r')
+  local file = io.open(opts.persistence.state_path, "r")
 
-  if (file ~= nil) then
-    local encoded = file:read('*a')
+  if file ~= nil then
+    local encoded = file:read("*a")
     file:close()
 
-    if (encoded ~= nil) then
+    if encoded ~= nil then
       M.state = vim.json.decode(encoded)
     end
   end
 
   -- ensure we have a UID
-  M.state.tree.uid = M.state.tree.uid or vim.fn.strftime('%Y%m%d%H%M%S')
+  M.state.tree.uid = M.state.tree.uid or vim.fn.strftime("%Y%m%d%H%M%S")
 
   for _, tree in ipairs(M.state.projects) do
-    tree.uid = tree.uid or vim.fn.strftime('%Y%m%d%H%M%S')
+    tree.uid = tree.uid or vim.fn.strftime("%Y%m%d%H%M%S")
   end
 end
 
 -- Save the main state.
 M.save_main_state = function(opts)
-  if (opts.persistence.state_path == nil) then
+  if opts.persistence.state_path == nil then
     return
   end
 
@@ -113,11 +113,11 @@ M.save_main_state = function(opts)
     state_path:touch({ parents = true })
   end
 
-  local file = io.open(opts.persistence.state_path, 'w')
+  local file = io.open(opts.persistence.state_path, "w")
 
-  if (file == nil) then
+  if file == nil then
     notify(
-      string.format('cannot save main state at %s', opts.persistence.state_path),
+      string.format("cannot save main state at %s", opts.persistence.state_path),
       vim.log.levels.ERROR
     )
   else
@@ -133,22 +133,22 @@ M.load_local_state = function()
   M.local_tree = nil
 
   local cwd = vim.fn.getcwd()
-  local local_mind = path:new(cwd, '.mind')
-  if (local_mind:is_dir()) then
+  local local_mind = path:new(cwd, ".mind")
+  if local_mind:is_dir() then
     -- we have a local mind; read the projects state from there
-    local file = io.open(path:new(cwd, '.mind', 'state.json'):expand(), 'r')
+    local file = io.open(path:new(cwd, ".mind", "state.json"):expand(), "r")
 
-    if (file == nil) then
-      notify('cannot open local Mind tree')
+    if file == nil then
+      notify("cannot open local Mind tree")
     else
-      local encoded = file:read('*a')
+      local encoded = file:read("*a")
       file:close()
 
-      if (encoded ~= nil) then
+      if encoded ~= nil then
         M.local_tree = vim.json.decode(encoded)
 
         -- ensure we have a UID
-        M.local_tree.uid = M.local_tree.uid or vim.fn.strftime('%Y%m%d%H%M%S')
+        M.local_tree.uid = M.local_tree.uid or vim.fn.strftime("%Y%m%d%H%M%S")
 
         M.local_cwd = cwd
       end
@@ -162,25 +162,34 @@ M.save_local_state = function()
     local cwd = vim.fn.getcwd()
 
     if M.local_cwd and cwd ~= M.local_cwd then
-      notify('refusing to save local state: differs from when it was loaded', vim.log.levels.ERROR)
-      notify(string.format('hint: loaded as %s, try saving as %s', M.local_cwd, cwd), vim.log.levels.INFO)
-      notify(string.format('hint: cd to %s in order to save the tree', M.local_cwd), vim.log.levels.INFO)
+      notify(
+        "refusing to save local state: differs from when it was loaded",
+        vim.log.levels.ERROR
+      )
+      notify(
+        string.format("hint: loaded as %s, try saving as %s", M.local_cwd, cwd),
+        vim.log.levels.INFO
+      )
+      notify(
+        string.format("hint: cd to %s in order to save the tree", M.local_cwd),
+        vim.log.levels.INFO
+      )
       return
     end
 
-    local local_mind = path:new(cwd, '.mind')
+    local local_mind = path:new(cwd, ".mind")
 
     -- ensure the path exists
     if not local_mind:exists() then
       local_mind:mkdir({ parents = true })
     end
 
-    if (local_mind:is_dir()) then
+    if local_mind:is_dir() then
       -- we have a local mind
-      local file = io.open(path:new(cwd, '.mind', 'state.json'):expand(), 'w')
+      local file = io.open(path:new(cwd, ".mind", "state.json"):expand(), "w")
 
-      if (file == nil) then
-        notify(string.format('cannot save local project at %s', cwd), 4)
+      if file == nil then
+        notify(string.format("cannot save local project at %s", cwd), 4)
       else
         local encoded = vim.json.encode(M.local_tree)
         file:write(encoded)
@@ -208,7 +217,7 @@ M.get_project_data_dir = function(use_global, opts)
     return opts.persistence.data_dir
   end
 
-  return '.mind/data'
+  return ".mind/data"
 end
 
 return M
diff --git a/lua/mind/ui.lua b/lua/mind/ui.lua
index e34937e..7388961 100644
--- a/lua/mind/ui.lua
+++ b/lua/mind/ui.lua
@@ -1,7 +1,7 @@
 -- Everything relating to the UI.
 local M = {}
 
-local mind_node = require'mind.node'
+local mind_node = require("mind.node")
 
 -- A per-tree render cache.
 --
@@ -14,25 +14,25 @@ M.render_cache = {}
 
 -- Get the highlight group to use for a node given its status.
 local function node_hl(node)
-  if (node.type == mind_node.TreeType.ROOT) then
-    return 'MindNodeRoot'
-  elseif (node.type == mind_node.TreeType.LOCAL_ROOT) then
-    return 'MindNodeRoot'
-  elseif (node.children ~= nil) then
-    return 'MindNodeParent'
+  if node.type == mind_node.TreeType.ROOT then
+    return "MindNodeRoot"
+  elseif node.type == mind_node.TreeType.LOCAL_ROOT then
+    return "MindNodeRoot"
+  elseif node.children ~= nil then
+    return "MindNodeParent"
   else
-    return 'MindNodeLeaf'
+    return "MindNodeLeaf"
   end
 end
 
 -- Compute the text line to display for a given node
 local function node_to_line(node, opts)
-  local name = ''
+  local name = ""
   local partial_hls = {}
 
   local node_group = node_hl(node)
   -- the icon goes first
-  if (node.icon ~= nil) then
+  if node.icon ~= nil then
     name = node.icon
     partial_hls[#partial_hls + 1] = {
       group = node_group,
@@ -46,56 +46,56 @@ local function node_to_line(node, opts)
 
     partial_hls[#partial_hls + 1] = {
       group = node_group,
-      width = #content.text
+      width = #content.text,
     }
   end
 
   -- special case for the first highlight:
-  if (node.type == nil) then
-    if (node.children ~= nil) then
-      partial_hls[#partial_hls - #node.contents + 1].group = 'MindNodeParent'
-    elseif (node.data == nil and node.url == nil) then
-      partial_hls[#partial_hls - #node.contents + 1].group = 'MindModifierEmpty'
+  if node.type == nil then
+    if node.children ~= nil then
+      partial_hls[#partial_hls - #node.contents + 1].group = "MindNodeParent"
+    elseif node.data == nil and node.url == nil then
+      partial_hls[#partial_hls - #node.contents + 1].group = "MindModifierEmpty"
     end
   end
 
   -- special marker for local roots
-  if (node.type == mind_node.TreeType.LOCAL_ROOT) then
-    local marker = ' ' .. opts.ui.local_marker
+  if node.type == mind_node.TreeType.LOCAL_ROOT then
+    local marker = " " .. opts.ui.local_marker
     name = name .. marker
 
     partial_hls[#partial_hls + 1] = {
-      group = 'MindLocalMarker',
+      group = "MindLocalMarker",
       width = #marker,
     }
   end
 
   -- special marker for data / URL nodes
   if node.data ~= nil then
-    local marker = ' ' .. opts.ui.data_marker
+    local marker = " " .. opts.ui.data_marker
     name = name .. marker
 
     partial_hls[#partial_hls + 1] = {
-      group = 'MindDataMarker',
+      group = "MindDataMarker",
       width = #marker,
     }
   elseif node.url ~= nil then
-    local marker = ' ' .. opts.ui.url_marker
+    local marker = " " .. opts.ui.url_marker
     name = name .. marker
 
     partial_hls[#partial_hls + 1] = {
-      group = 'MindURLMarker',
+      group = "MindURLMarker",
       width = #marker,
     }
   end
 
   -- special marker for selection
-  if (node.is_selected) then
-    local marker = ' ' .. opts.ui.select_marker
+  if node.is_selected then
+    local marker = " " .. opts.ui.select_marker
     name = name .. marker
 
     partial_hls[#partial_hls + 1] = {
-      group = 'MindSelectMarker',
+      group = "MindSelectMarker",
       width = #marker,
     }
   end
@@ -114,12 +114,12 @@ local function render_node(node, indent, is_last, lines, hls, opts)
       line = indent
       indent = indent
     else
-      line = indent .. opts.ui.node_indent_marker .. ' '
-      indent = indent .. '  '
+      line = indent .. opts.ui.node_indent_marker .. " "
+      indent = indent .. "  "
     end
   else
-    line = indent .. opts.ui.empty_indent_marker .. ' '
-    indent = indent .. opts.ui.empty_indent_marker .. ' '
+    line = indent .. opts.ui.empty_indent_marker .. " "
+    indent = indent .. opts.ui.empty_indent_marker .. " "
   end
 
   local name, partial_hls = node_to_line(node, opts)
@@ -127,22 +127,22 @@ local function render_node(node, indent, is_last, lines, hls, opts)
   local hl_line = #lines
 
   hls[#hls + 1] = {
-    group = 'MindOpenMarker',
+    group = "MindOpenMarker",
     line = hl_line,
     col_start = 0,
     col_end = #line,
   }
 
-  if (node.children ~= nil) then
-    if (node.is_expanded) then
-      local mark = ' '
+  if node.children ~= nil then
+    if node.is_expanded then
+      local mark = " "
       local hl_col_end = hl_col_start + #mark
 
       hls[#hls + 1] = {
-        group = 'MindOpenMarker',
+        group = "MindOpenMarker",
         line = hl_line,
         col_start = hl_col_start,
-        col_end = hl_col_end
+        col_end = hl_col_end,
       }
 
       lines[#lines + 1] = line .. mark .. name
@@ -155,7 +155,7 @@ local function render_node(node, indent, is_last, lines, hls, opts)
           group = hl.group,
           line = hl_line,
           col_start = hl_col_start,
-          col_end = hl_col_end
+          col_end = hl_col_end,
         }
       end
 
@@ -165,14 +165,14 @@ local function render_node(node, indent, is_last, lines, hls, opts)
       end
       render_node(node.children[#node.children], indent, true, lines, hls, opts)
     else
-      local mark = ' '
+      local mark = " "
       local hl_col_end = hl_col_start + #mark
 
       hls[#hls + 1] = {
-        group = 'MindClosedMarker',
+        group = "MindClosedMarker",
         line = hl_line,
         col_start = hl_col_start,
-        col_end = hl_col_end
+        col_end = hl_col_end,
       }
 
       lines[#lines + 1] = line .. mark .. name
@@ -184,7 +184,7 @@ local function render_node(node, indent, is_last, lines, hls, opts)
           group = hl.group,
           line = hl_line,
           col_start = hl_col_start,
-          col_end = hl_col_end
+          col_end = hl_col_end,
         }
       end
     end
@@ -195,7 +195,12 @@ local function render_node(node, indent, is_last, lines, hls, opts)
     for _, hl in ipairs(partial_hls) do
       hl_col_start = hl_col_end
       hl_col_end = hl_col_start + hl.width
-      hls[#hls + 1] = { group = hl.group, line = hl_line, col_start = hl_col_start, col_end = hl_col_end }
+      hls[#hls + 1] = {
+        group = hl.group,
+        line = hl_line,
+        col_start = hl_col_start,
+        col_end = hl_col_end,
+      }
     end
   end
 end
@@ -204,7 +209,7 @@ end
 local function render_tree(tree, opts)
   local lines = {}
   local hls = {}
-  render_node(tree, '', true, lines, hls, opts)
+  render_node(tree, "", true, lines, hls, opts)
   return lines, hls
 end
 
@@ -282,7 +287,7 @@ end
 -- Ask the user for input with a given prompt and run the tree function on it.
 M.with_input = function(prompt, default, f)
   vim.ui.input({ prompt = prompt, default = default }, function(input)
-    if (input ~= nil) then
+    if input ~= nil then
       f(input)
     end
   end)
diff --git a/stylua.toml b/stylua.toml
new file mode 100644
index 0000000..421c3d9
--- /dev/null
+++ b/stylua.toml
@@ -0,0 +1,3 @@
+indent_type = "Spaces"
+indent_width = 2
+column_width = 80