diff --git a/init.el b/init.el
index 34ee03b..4ae106f 100644
--- a/init.el
+++ b/init.el
@@ -64,7 +64,7 @@
  ;; Your init file should contain only one such instance.
  ;; If there is more than one, they won't work right.
  '(package-selected-packages
-   '(helpful lsp-haskell dashboard fsharp-mode dash-at-point racer racer-mode flycheck-rust rust-mode haskell-mode dune which-key erlang gitignore-mode yaml-mode nginx-mode ansible terraform-mode dockerfile-mode reason-mode merlin tuareg clj-refactor cider clojure-mode elixir-mode js2-mode web-mode enh-ruby-mode ruby-end rspec-mode planet-theme flatui-theme base16-theme smart-mode-line lsp-ui lsp-mode deft counsel-projectile flycheck company yasnippet-snippets yasnippet visual-regexp column-enforce-mode rainbow-mode rainbow-delimiters magit hydra counsel keyfreq exec-path-from-shell buffer-move use-package))
+   '(undo-tree helpful lsp-haskell dashboard fsharp-mode dash-at-point racer racer-mode flycheck-rust rust-mode haskell-mode dune which-key erlang gitignore-mode yaml-mode nginx-mode ansible terraform-mode dockerfile-mode reason-mode merlin tuareg clj-refactor cider clojure-mode elixir-mode js2-mode web-mode enh-ruby-mode ruby-end rspec-mode planet-theme flatui-theme base16-theme smart-mode-line lsp-ui lsp-mode deft counsel-projectile flycheck company yasnippet-snippets yasnippet visual-regexp column-enforce-mode rainbow-mode rainbow-delimiters magit hydra counsel keyfreq exec-path-from-shell buffer-move use-package))
  '(safe-local-variable-values
    '((haskell-process-use-ghci . t)
      (haskell-indent-spaces . 4))))
diff --git a/pkg/base.el b/pkg/base.el
index 2d346da..3fdd460 100644
--- a/pkg/base.el
+++ b/pkg/base.el
@@ -155,6 +155,18 @@
 (keyfreq-mode t)
 (keyfreq-autosave-mode t)
 
+;;;;;;;;;;;;;;;;; Use more advanced undo options
+(use-package undo-tree
+  :defer t
+  :ensure t
+  :config (setq-default
+           ;; Show diff
+           undo-tree-visualizer-diff t
+           ;; Show timestamps
+           undo-tree-visualizer-timestamps t))
+
+(global-undo-tree-mode t)
+
 ;;;;;;;;;;;;;;;;; Show hints about key combinations
 (use-package which-key
   :defer t
diff --git a/pkg/hydra.el b/pkg/hydra.el
index 38c7547..3ddadc9 100644
--- a/pkg/hydra.el
+++ b/pkg/hydra.el
@@ -43,7 +43,7 @@ _d_: Deft                       _c_: Invalidate cache
 ^^^^^^^^-----------------------------------------------------------------------
 _c_: Comment line      _y_: Yasnippet
 _r_: Regex replace     _m_: Company
-_i_: Indent region
+_i_: Indent region     _u_: Undo tree
 _a_: Align regexp
 _e_: Eval region
 _s_: Swiper
@@ -57,6 +57,7 @@ _s_: Swiper
     ("e"  eval-region)
     ("s"  swiper)
 
+    ("u"  undo-tree-visualize)
     ("y"  company-yasnippet)
     ("m"  company-complete))
 
diff --git a/themes/themes.el b/themes/themes.el
index be1adc6..df7369a 100644
--- a/themes/themes.el
+++ b/themes/themes.el
@@ -46,8 +46,11 @@
 (defun set-font-to-screen ()
   "Automatically set font size to suit the monitor."
   (interactive)
+  ;; If display is set to emulate FullHD resultion or less, make the font
+  ;; smaller.
   (if (>= 1080 (x-display-pixel-height))
       (set-font "Hack" 13)
+    ;; Else, set to default size.
     (set-font "Hack" 16)))
 
 ;; Do it automatically on startup