diff --git a/NEWS.md b/NEWS.md
index 3bade25..c7a875b 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,9 @@
 # revealjs (development version)
 
+## OTHER CHANGES
+
+- `ids` theme: second- and higher-level list items are now rendered progressively smaller (each nesting level at 80% of its parent), emphasising list hierarchy as in the IDS reference decks.
+
 ## REVEAL JS LIBRARY UPDATE
 
 This version of the package comes with reveal.js v4 which is a major update from previous reveal.js v3. Built-in plugins (`zoom`, `search` and `notes`) have been updated, as well as third party plugin included in this package (`menu` and `chalkboard`). A lot of bugfixes and improvements have been made in the upstream library and now the R package can benefit from it. However, this cause also some breaking changes for **revealjs** R package that we described below.
diff --git a/examples/ids.Rmd b/examples/ids.Rmd
index a7e62f7..013b7bc 100644
--- a/examples/ids.Rmd
+++ b/examples/ids.Rmd
@@ -45,6 +45,10 @@
 
 - Bullet 1
 - Bullet 2
+  - Second-level bullet
+  - Second-level bullet
+    - Third-level bullet
+    - Third-level bullet
 - Bullet 3
 
 <aside class="notes">
diff --git a/inst/reveal.js-5.1.0/css/theme/source/ids.scss b/inst/reveal.js-5.1.0/css/theme/source/ids.scss
index e97f0c7..b069d58 100644
--- a/inst/reveal.js-5.1.0/css/theme/source/ids.scss
+++ b/inst/reveal.js-5.1.0/css/theme/source/ids.scss
@@ -269,6 +269,16 @@
   }
 }
 
+// Nested list items are set progressively smaller, both to emphasise the
+// hierarchy and to keep deeply nested lists from visually competing with the
+// first level. The em size compounds down the nesting levels, so each deeper
+// level is 80% of its parent (level 2: 80%, level 3: 64%, level 4: 51%).
+// Markers and the hanging indentation (padding-left: 0.7em above) scale with
+// the text automatically.
+.reveal li li {
+  font-size: 0.8em;
+}
+
 
 /*********************************************
  * FOOTER
diff --git a/inst/reveal.js-5.1.0/dist/theme/ids.css b/inst/reveal.js-5.1.0/dist/theme/ids.css
index ef9e1f5..3a5dcb0 100644
--- a/inst/reveal.js-5.1.0/dist/theme/ids.css
+++ b/inst/reveal.js-5.1.0/dist/theme/ids.css
@@ -482,6 +482,15 @@
   color: var(--r-list-bullet-color) !important;
 }
 
+/* Nested list items are set progressively smaller, both to emphasise the
+   hierarchy and to keep deeply nested lists from visually competing with the
+   first level. The em size compounds down the nesting levels, so each deeper
+   level is 80% of its parent (level 2: 80%, level 3: 64%, level 4: 51%).
+   Markers and the hanging indentation scale with the text automatically. */
+.reveal li li {
+  font-size: 0.8em;
+}
+
 /*********************************************
  * FOOTER
  *********************************************/