diff --git a/inst/reveal.js-5.2.1/css/theme/source/ids.scss b/inst/reveal.js-5.2.1/css/theme/source/ids.scss
index 05952f8..e83f1ad 100644
--- a/inst/reveal.js-5.2.1/css/theme/source/ids.scss
+++ b/inst/reveal.js-5.2.1/css/theme/source/ids.scss
@@ -269,14 +269,21 @@
 // bar keeps the same height and the body content starts at the same place on
 // every slide. :has() is what lets us ask "is a subtitle coming?" in CSS; where
 // it is unsupported such slides simply keep a title-height bar.
+//
+// The lone title is vertically CENTRED in its reserved bar: half of the
+// reservation goes above the text as top padding (the bar segment, anchored
+// to the heading box, moves up with it), and the bottom half stays in the bar
+// extension plus margin. The space consumed below the bar is reduced by the
+// same half, so body content starts where it always did.
 .reveal .slides section:not(.title-frame) > h1:first-child:not(:has(+ h3)),
 .reveal .slides section:not(.title-frame) > h2:first-child:not(:has(+ h3)) {
-  margin-bottom: calc(#{$idsHeadingSpacing} + #{$idsSubtitleHeight} + #{$blockMargin}) !important;
+  padding-top: calc((#{$idsHeadingSpacing} + #{$idsSubtitleHeight}) / 2) !important;
+  margin-bottom: calc((#{$idsHeadingSpacing} + #{$idsSubtitleHeight}) / 2 + #{$blockMargin}) !important;
 }
 
 .reveal .slides section:not(.title-frame) > h1:first-child:not(:has(+ h3))::before,
 .reveal .slides section:not(.title-frame) > h2:first-child:not(:has(+ h3))::before {
-  height: calc(100% + #{$idsHeadingSpacing} + #{$idsSubtitleHeight}) !important;
+  height: calc(100% + (#{$idsHeadingSpacing} + #{$idsSubtitleHeight}) / 2) !important;
 }
 
 // The subtitle sits in the slide's normal text column, so its segment has to