diff --git a/assets/_custom.scss b/assets/_custom.scss
new file mode 100644
index 0000000..aa9199e
--- /dev/null
+++ b/assets/_custom.scss
@@ -0,0 +1,37 @@
+.book-page {
+	box-shadow: 0px -1.5rem 1.5rem rgba(0, 0, 0, 0.15);
+	padding-left: 2rem;
+	padding-right: 2rem;
+}
+
+.book-menu .book-menu-content {
+	padding-right: 1.5rem;
+}
+
+.book-toc .book-toc-content {
+	padding-left: 1.5rem;
+}
+
+.markdown h1 {
+	font-weight: bold;
+}
+
+.markdown h2 {
+	margin-top: 1.5em;
+	font-weight: bold;
+	font-size: 1.7em;
+}
+
+.markdown h3 {
+	margin-top: 1.5em;
+	font-weight: bold;
+	font-size: 1.25em;
+}
+
+.container {
+	max-width: 90rem;
+}
+
+summary:focus {
+	outline: none;
+}