Add header margin change

to be more generic

book.toml

@@ -33,7 +33,7 @@ site-url = "/synapse/"
 additional-css = [
     "docs/website_files/table-of-contents.css",
     "docs/website_files/remove-nav-buttons.css",
-    "docs/website_files/indent-section-headers.css",
+    "docs/website_files/section-headers.css",
 ]
 additional-js = ["docs/website_files/table-of-contents.js"]
 theme = "docs/website_files/theme"

docs/website_files/indent-section-headers.css

@@ -1,7 +0,0 @@
-/*
- * Indents each chapter title in the left sidebar so that they aren't
- * at the same level as the section headers.
- */
-.chapter-item {
-    margin-left: 1em;
-}

docs/website_files/section-headers.css

@@ -0,0 +1,20 @@
+/*
+ * Indents each chapter title in the left sidebar so that they aren't
+ * at the same level as the section headers.
+ */
+.chapter-item {
+    margin-left: 1em;
+}
+
+/*
+ * Prevents a large gap between successive section headers.
+ *
+ * mdbook sets 'margin-top: 2.5em' on h2 and h3 headers. This makes sense when separating
+ * a header from the paragraph beforehand, but has the downside of introducing a large
+ * gap between headers that are next to each other with no text in between.
+ *
+ * This rule reduces the margin in this case.
+ */
+ h1 + h2, h2 + h3 {
+    margin-top: 1.0em;
+ }