diff --git a/docs/conf.py b/docs/conf.py
index dfc2942..0091b38 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -73,7 +73,22 @@
 #html_theme_path = jupyter_sphinx_theme.get_html_theme_path()
 
 # --- karma ---
-html_theme = "karma_sphinx_theme"
+#html_theme = "karma_sphinx_theme"
+
+# --- material ---
+html_theme = "sphinx_material"
+# Material theme options (see theme.conf for more information)
+html_theme_options = {
+    # Visible levels of the global TOC; -1 means unlimited
+    'globaltoc_depth': 2,
+    # If False, expand all TOC entries
+    'globaltoc_collapse': True,
+    # If True, show hidden TOC entries
+    'globaltoc_includehidden': True,
+}
+html_sidebars = {
+    "**": ["globaltoc.html"]
+}
 
 # --- custom css ---
 html_title       = project
diff --git a/docs/requirements.txt b/docs/requirements.txt
index a25e1cf..9b03960 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,11 +1,9 @@
-Sphinx==2.2.1
-sphinxcontrib-applehelp==1.0.1
-sphinxcontrib-devhelp==1.0.1
-sphinxcontrib-htmlhelp==1.0.2
-sphinxcontrib-jsmath==1.0.1
-sphinxcontrib-qthelp==1.0.2
-sphinxcontrib-serializinghtml==1.1.3
-sphinx_materialdesign_theme
-jupyter-sphinx-theme
-karma_sphinx_theme
+Sphinx
+sphinxcontrib-applehelp
+sphinxcontrib-devhelp
+sphinxcontrib-htmlhelp
+sphinxcontrib-jsmath
+sphinxcontrib-qthelp
+sphinxcontrib-serializinghtml
+sphinx-material
 sphinx-copybutton