diff --git a/css/dist/reveal.css b/css/dist/pretext-reveal.css
similarity index 89%
rename from css/dist/reveal.css
rename to css/dist/pretext-reveal.css
index 16e1d787f0..ff434df4d2 100644
--- a/css/dist/reveal.css
+++ b/css/dist/pretext-reveal.css
@@ -34,15 +34,13 @@ ul.circle {
 ul {
   display: block !important;
 }
-dfn {
-  font-weight: bold;
-}
 .cols1 li,
 .cols2 li,
 .cols3 li,
 .cols4 li,
 .cols5 li,
 .cols6 li {
+  float: left;
   padding-right: 2em;
 }
 .definition-like,
@@ -51,7 +49,7 @@ dfn {
 .project-like {
   border-width: 0.5px;
   border-style: solid;
-  border-radius: 2px 10px;
+  border-radius: 2px 10px 2px;
   padding: 1%;
   margin-bottom: var(--r-block-margin);
 }
@@ -72,18 +70,24 @@ dfn {
   border-radius: 2px 10px;
   padding: 4px;
 }
-.ptx-content :is(.image-box, .audio-box, .video-box, .asymptote-box) {
+.image-box,
+.audio-box,
+.video-box,
+.asymptote-box {
   position: relative;
 }
-.ptx-content iframe.asymptote,
-.ptx-content .video-box .video,
-.ptx-content .video-box .video-poster {
+iframe.asymptote,
+.video-box .video,
+.video-box .video-poster {
   position: absolute;
   top: 0;
   left: 0;
   width: 100%;
   height: 100%;
 }
+div[style*="display:table-cell"] img {
+  width: 100%;
+}
 .code-inline {
   background: color-mix(in srgb, var(--r-background-color) 75%, var(--r-link-color));
   padding: 0 3px;
@@ -96,20 +100,6 @@ dfn {
   color: black;
   border: 0.5px solid var(--r-main-color);
 }
-.reveal pre {
-  box-shadow: none;
-  line-height: 1;
-  font-size: inherit;
-  width: auto;
-  margin: inherit;
-}
-.reveal pre code {
-  display: block;
-  padding: 0;
-  overflow: unset;
-  max-height: unset;
-  word-wrap: normal;
-}
 .program {
   background: color-mix(in srgb, var(--r-background-color) 75%, var(--r-link-color));
   max-height: 450px;
@@ -125,5 +115,22 @@ pre[class*=language-] {
   padding: 0;
   line-height: 1.2;
 }
+.reveal pre {
+  box-shadow: none;
+  line-height: 1;
+  font-size: inherit;
+  width: auto;
+  margin: inherit;
+}
+.reveal pre code {
+  display: block;
+  padding: 0;
+  overflow: unset;
+  max-height: unset;
+  word-wrap: normal;
+}
+dfn {
+  font-weight: bold;
+}
 /*! Theme: reveal */
-/*# sourceMappingURL=reveal.css.map */
+/*# sourceMappingURL=pretext-reveal.css.map */
diff --git a/css/targets/revealjs/reveal.scss b/css/targets/revealjs/reveal.scss
index 3513955371..d20bf68c79 100644
--- a/css/targets/revealjs/reveal.scss
+++ b/css/targets/revealjs/reveal.scss
@@ -1,23 +1,27 @@
 /*! Theme: reveal */
+
+// Tip: to build just this file directly to a folder for testing, do something like:
+// npm run build -- -w -t pretext-reveal -o ../../examples/sample-slideshow/out/_static/pretext/css
+
 @use "components/elements/list-styles";
 
+//---- List Styles ----
 ul {
   display: block !important;
 }
 
-dfn {
-  font-weight: bold;
-}
-
 .cols1 li,
 .cols2 li,
 .cols3 li,
 .cols4 li,
 .cols5 li,
 .cols6 li {
+  float: left;
   padding-right: 2em;
 }
 
+//---- Container Styles ----
+
 /* Callout boxes */
 // Note: the box around a "theorem" does not contain
 // the associated "proof" because the HTML does not
@@ -28,7 +32,7 @@ dfn {
 .project-like {
   border-width: 0.5px;
   border-style: solid;
-  border-radius: 2px 10px;
+  border-radius: 2px 10px 2px;
   padding: 1%;
   margin-bottom: var(--r-block-margin);
 }
@@ -49,20 +53,23 @@ dfn {
   background: color-mix(in srgb, var(--r-background-color) 75%, #608000);
 }
 
-/* Image-like */
+//---- Media Styles ----
 .reveal img {
   border: 0.5px !important;
   border-radius: 2px 10px;
   padding: 4px;
 }
 
-.ptx-content :is(.image-box, .audio-box, .video-box, .asymptote-box) {
+.image-box,
+.audio-box,
+.video-box,
+.asymptote-box {
   position: relative;
 }
 
-.ptx-content iframe.asymptote,
-.ptx-content .video-box .video,
-.ptx-content .video-box .video-poster {
+iframe.asymptote,
+.video-box .video,
+.video-box .video-poster {
   position: absolute;
   top: 0;
   left: 0;
@@ -70,7 +77,13 @@ dfn {
   height: 100%;
 }
 
-/* Code-like blocks */
+// make small images full-width in #sidebyside
+// could improve with a .sidebyside class
+div[style*="display:table-cell"] img {
+    width: 100%;
+}
+
+//---- Codelike Styles ----
 .code-inline {
   background: color-mix(in srgb, var(--r-background-color) 75%, var(--r-link-color));
   padding: 0 3px;
@@ -85,22 +98,6 @@ dfn {
   border: 0.5px solid var(--r-main-color);
 }
 
-.reveal pre {
-  box-shadow: none;
-  line-height: 1;
-  font-size: inherit;
-  width: auto;
-  margin: inherit;
-}
-
-.reveal pre code {
-  display: block;
-  padding: 0;
-  overflow: unset;
-  max-height: unset;
-  word-wrap: normal;
-}
-
 .program {
   background: color-mix(in srgb, var(--r-background-color) 75%, var(--r-link-color));
   max-height: 450px;
@@ -117,4 +114,26 @@ code[class*="language-"],
 pre[class*="language-"] {
   padding: 0;
   line-height: 1.2;
+}
+
+// Undo some reveal.js defaults
+.reveal pre {
+  box-shadow: none;
+  line-height: 1;
+  font-size: inherit;
+  width: auto;
+  margin: inherit;
+}
+
+.reveal pre code {
+  display: block;
+  padding: 0;
+  overflow: unset;
+  max-height: unset;
+  word-wrap: normal;
+}
+
+//---- Other Styles ----
+dfn {
+  font-weight: bold;
 }
\ No newline at end of file
diff --git a/doc/guide/publisher/publication-file.xml b/doc/guide/publisher/publication-file.xml
index d91524d7bb..6d4c62d9fe 100644
--- a/doc/guide/publisher/publication-file.xml
+++ b/doc/guide/publisher/publication-file.xml
@@ -857,8 +857,9 @@
 
             <p>The<cd>
                 <cline>/publication/revealjs/appearance</cline>
-            </cd>element can have the following attribute:<ul>
-                <li><attr>theme</attr>: the base name of a file that is a reveal.js theme.  For example if the desired theme/CSS file is <c>css/theme/solarized.css</c>, then set the value of this attribute to <c>solarized</c>.</li>
+            </cd>element can have the following attributes:<ul>
+                <li><attr>theme</attr>: the base name of a file that is a reveal.js theme. (See the <url href="https://revealjs.com/themes/">reveal.js documentation</url> for available themes.)  For example if the desired theme/CSS file is <c>css/theme/solarized.css</c>, then set the value of this attribute to <c>solarized</c>.</li>
+                <li><attr>custom-css</attr>: a string separated list of custom css files to load. These may be local files or remote URLs. For local files, it is recommended to place them in the <term>external</term> files directory so that they are automatically copied from your source folder to the output directory. (Refer to <xref ref="processing-directory-management"/> for more information on external files.)</li>
             </ul></p>
         </subsection>
 
diff --git a/examples/sample-slideshow/external/custom.css b/examples/sample-slideshow/external/custom.css
new file mode 100644
index 0000000000..05e266f734
--- /dev/null
+++ b/examples/sample-slideshow/external/custom.css
@@ -0,0 +1,5 @@
+/* Sample of custom CSS to override/extend defaults */
+
+.reveal h4 {
+  color: #3b658f;
+}
\ No newline at end of file
diff --git a/examples/sample-slideshow/publication.xml b/examples/sample-slideshow/publication.xml
index 13a0d7429c..04028d2936 100644
--- a/examples/sample-slideshow/publication.xml
+++ b/examples/sample-slideshow/publication.xml
@@ -28,7 +28,13 @@ along with PreTeXt.  If not, see <http://www.gnu.org/licenses/>.
     </source>
 
     <revealjs>
-        <appearance theme="solarized"/>
+        <!-- theme="solarized" is the default, see https://revealjs.com/themes/ -->
+        <!-- for other theme options.                                           -->
+        <!-- custom-css is a space-separated list of CSS files to include.      -->
+        <!-- They can be local or remote. If local, they should be under your   -->
+        <!-- "external files" directory if you want them automatically copied   -->
+        <!-- to the output folder.                                              -->
+        <appearance theme="solarized" custom-css="external/custom.css"/>
         <!-- this is a "resources" default, but best for a sample -->
         <resources host="cdn"/>
         <!-- display="yes" is the default so we can see arrows          -->
diff --git a/pretext/lib/pretext.py b/pretext/lib/pretext.py
index 3cdefe64e5..b5439c26cc 100644
--- a/pretext/lib/pretext.py
+++ b/pretext/lib/pretext.py
@@ -4264,8 +4264,18 @@ def revealjs(
     copy_managed_directories(tmp_dir, external_abs=external_abs, generated_abs=generated_abs)
 
     # place JS in scratch directory
+    # TODO: audit what JS is really needed/used
     copy_html_js(tmp_dir)
 
+    # copy CSS
+    css_src = os.path.join(get_ptx_path(), "css", "dist", "pretext-reveal.css")
+    css_dest = os.path.join(tmp_dir, "_static", "pretext", "css", "pretext-reveal.css")
+    with open(css_src, 'r') as theme_file:
+        filedata = theme_file.read()
+        os.makedirs(os.path.dirname(css_dest), exist_ok=True)
+        with open(css_dest, 'w+') as file:
+            file.write(filedata)
+
     # Write output into temporary directory
     log.info("converting {} to HTML in {}".format(xml, tmp_dir))
     derivedname = get_output_filename(xml, out_file, dest_dir, ".html")
diff --git a/script/cssbuilder/cssbuilder.mjs b/script/cssbuilder/cssbuilder.mjs
index 63e51c58a6..2081815d09 100644
--- a/script/cssbuilder/cssbuilder.mjs
+++ b/script/cssbuilder/cssbuilder.mjs
@@ -119,7 +119,7 @@ function getTargets(options) {
     { out: 'theme-tacoma', in: path.join(cssRoot, 'targets/html/tacoma/theme-tacoma.scss') },
     // -------------------------------------------------------------------------
     // Non-web targets
-    { out: 'reveal', in: path.join(cssRoot, 'targets/revealjs/reveal.scss')},
+    { out: 'pretext-reveal', in: path.join(cssRoot, 'targets/revealjs/reveal.scss')},
     { out: 'kindle', in: path.join(cssRoot, 'targets/ebook/kindle/kindle.scss')},
     { out: 'epub', in: path.join(cssRoot, 'targets/ebook/epub/epub.scss')},
   ]
@@ -157,8 +157,9 @@ function getTargets(options) {
           // Modules build directly to destination with no subfolder
           targets[0].out = targets[0].out.replace('modules/', '');
         } else {
-          // Others build as theme.css
-          targets[0].out = 'theme';
+          // Individual HTML theme files build as theme.css
+          if(targets[0].in.includes("theme-"))
+              targets[0].out = 'theme';
         }
       }
     }
diff --git a/xsl/pretext-html.xsl b/xsl/pretext-html.xsl
index 209b33a8bb..f1833a0e6d 100644
--- a/xsl/pretext-html.xsl
+++ b/xsl/pretext-html.xsl
@@ -208,6 +208,9 @@ along with MathBook XML.  If not, see <http://www.gnu.org/licenses/>.
 <xsl:param name="html.presentation" select="'no'" />
 <xsl:variable name="b-html-presentation" select="$html.presentation = 'yes'" />
 
+<!-- Used to identify if target is reveal.js instead of vanilla html -->
+<xsl:variable name="b-reveal-build" select="false()" />
+
 <!-- ############### -->
 <!-- Source Analysis -->
 <!-- ############### -->
@@ -13261,7 +13264,7 @@ TODO:
         <script src="https://cdnjs.cloudflare.com/ajax/libs/prism/1.26.0/plugins/autoloader/prism-autoloader.min.js"></script>
         <script src="https://cdnjs.cloudflare.com/ajax/libs/prism/1.26.0/plugins/line-numbers/prism-line-numbers.min.js" integrity="sha512-dubtf8xMHSQlExGRQ5R7toxHLgSDZ0K7AunqPWHXmJQ8XyVIG19S1T95gBxlAeGOK02P4Da2RTnQz0Za0H0ebQ==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>
         <script src="https://cdnjs.cloudflare.com/ajax/libs/prism/1.26.0/plugins/line-highlight/prism-line-highlight.min.js" integrity="sha512-93uCmm0q+qO5Lb1huDqr7tywS8A2TFA+1/WHvyiWaK6/pvsFl6USnILagntBx8JnVbQH5s3n0vQZY6xNthNfKA==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>
-        <xsl:if test="$b-html-theme-legacy">
+        <xsl:if test="$b-html-theme-legacy or $b-reveal-build" >
             <!-- Legacy themes rely on external css for prism, but newer ones have it built in -->
             <link href="https://cdnjs.cloudflare.com/ajax/libs/prism/1.26.0/themes/prism.css" rel="stylesheet"/>
             <!-- We could conditionally load the following based on line number -->
diff --git a/xsl/pretext-revealjs.xsl b/xsl/pretext-revealjs.xsl
index 793fa33170..b7d91969c8 100644
--- a/xsl/pretext-revealjs.xsl
+++ b/xsl/pretext-revealjs.xsl
@@ -33,7 +33,8 @@ along with PreTeXt.  If not, see <http://www.gnu.org/licenses/>.
     xmlns:pi="http://pretextbook.org/2020/pretext/internal"
     xmlns:exsl="http://exslt.org/common"
     xmlns:date="http://exslt.org/dates-and-times"
-    extension-element-prefixes="exsl date"
+    xmlns:str="http://exslt.org/strings"
+    extension-element-prefixes="exsl date str"
 >
 
 <!-- Necessary to get some HTML constructions,    -->
@@ -44,6 +45,10 @@ along with PreTeXt.  If not, see <http://www.gnu.org/licenses/>.
 <!-- entry template                               -->
 <xsl:import href="pretext-html.xsl" />
 
+<!-- Used to identify build target in templates shared with plain  -->
+<!-- HTML conversion                                               -->
+<xsl:variable name="b-reveal-build" select="true()" />
+
 <!-- HTML5 format -->
 <xsl:output method="html" indent="yes" encoding="UTF-8" doctype-system="about:legacy-compat"/>
 
@@ -111,154 +116,22 @@ along with PreTeXt.  If not, see <http://www.gnu.org/licenses/>.
             <script src="{$reveal-root}/reveal.js"></script>
             <script src="{$reveal-root}/plugin/math/math.js"></script>
 
-          <!--  Some style changes from regular pretext-html -->
-          <!-- Note: the box around a "theorem" does not contain -->
-          <!-- the associated "proof" because the HTML does not  -->
-          <!-- provide an enclosure containing both.             -->
+            <link href="_static/pretext/css/pretext-reveal.css" rel="stylesheet"></link>
           <style>
-ul {
-  display: block !important;
-}
-.reveal img {
-  border: 0.5px !important;
-  border-radius: 2px 10px 2px;
-  padding: 4px;
-}
-.reveal pre {
-  box-shadow: none;
-  line-height: 1;
-  font-size: inherit;
-  width: auto;
-  margin: inherit;
-}
-.reveal pre code {
-  display: block;
-  padding: 0;
-  overflow: unset;
-  max-height: unset;
-  word-wrap: normal;
-}
-.definition-like,.theorem-like,.project-like {
-  border-width: 0.5px;
-  border-style: solid;
-  border-radius: 2px 10px 2px;
-  padding: 1%;
-  margin-bottom: var(--r-block-margin);
-}
-.definition-like {
-  background: #006080;
-  background: color-mix(in srgb, var(--r-background-color) 75%, #006080);
-}
-.theorem-like {
-  background: #ff000010;
-  background:  color-mix(in srgb, var(--r-background-color) 75%, #aa0000);
-}
-.proof-like {
-  background: #ffffff;
-  background:  color-mix(in srgb, var(--r-background-color) 75%, #aaaaaa);
-}
-.project-like {
-  background: #60800010;
-  background:  color-mix(in srgb, var(--r-background-color) 75%, #608000);
-}
-.code-inline {
-  background: #60800010;
-  background:  color-mix(in srgb, var(--r-background-color) 75%, var(--r-link-color));
-  padding: 0 3px;
-  border: 1px solid;
-  margin: 3px;
-  display: inline-block;
-}
-.sagecell_sessionOutput {
-  background: white;
-  color: black;
-  border: 0.5px solid var(--r-main-color);
-}
-
-.program {
-  background: #60800010;
-  background:  color-mix(in srgb, var(--r-background-color) 75%, var(--r-link-color));
-  max-height: 450px;
-  overflow: auto;
-  border: 0.5px solid var(--r-main-color);
-}
-.ptx-sagecell, .reveal .program {
-  font-size: calc(var(--r-main-font-size) * 0.6);
-}
-
-
-.ptx-content :is(.image-box, .audio-box, .video-box, .asymptote-box) {
-  position: relative;
-}
-
-.ptx-content iframe.asymptote, .ptx-content iframe.asymptote, .ptx-content .video-box .video, .ptx-content .video-box .video-poster {
-  position: absolute;
-  top: 0;
-  left: 0;
-  width: 100%;
-  height: 100%;
-}
-
-
-code[class*="language-"], pre[class*="language-"] {
-  padding: 0;
-  line-height: 1.2;
-}
-
-dfn {
-  font-weight: bold;
-}
-.ptx-content ol.no-marker,
-.ptx-content ul.no-marker,
-.ptx-content li.no-marker {
-    list-style-type: none;
-}
-
-.ptx-content ol.decimal {
-    list-style-type: decimal;
-}
-.ptx-content ol.lower-alpha {
-    list-style-type: lower-alpha;
-}
-.ptx-content ol.upper-alpha {
-    list-style-type: upper-alpha;
-}
-.ptx-content ol.lower-roman {
-    list-style-type: lower-roman;
-}
-.ptx-content ol.upper-roman {
-    list-style-type: upper-roman;
-}
-.ptx-content ul.disc {
-    list-style-type: disc;
-}
-.ptx-content ul.square {
-    list-style-type: square;
-}
-.ptx-content ul.circle {
-    list-style-type: circle;
-}
-.ptx-content ol.no-marker,
-.ptx-content ul.no-marker {
-    list-style-type: none;
-}
-.ptx-content .cols1 li,
-.ptx-content .cols2 li,
-.ptx-content .cols3 li,
-.ptx-content .cols4 li,
-.ptx-content .cols5 li,
-.ptx-content .cols6 li {
-    float: left;
-    padding-right:2em;
-}
-
-/* make small images full-width in #sidebyside */
-/* could improve with a .sidebyside class */
-div[style*="display:table-cell"] img {
-    width: 100%;
-}
           </style>
           <xsl:call-template name="diagcess-header"/>
+          
+          <!-- custom-css, if specified, should be last -->
+          <xsl:if test="not($reveal-custom-css = '')">
+              <xsl:variable name="csses" select="str:tokenize($reveal-custom-css, ', ')"/>
+              <xsl:for-each select="$csses">
+                  <link rel="stylesheet" type="text/css">
+                      <xsl:attribute name="href">
+                          <xsl:value-of select="." />
+                      </xsl:attribute>
+                  </link>
+              </xsl:for-each>
+          </xsl:if>
         </head>
 
         <body>
diff --git a/xsl/publisher-variables.xsl b/xsl/publisher-variables.xsl
index 9f7a2838a0..1eac392937 100644
--- a/xsl/publisher-variables.xsl
+++ b/xsl/publisher-variables.xsl
@@ -3043,6 +3043,11 @@ along with PreTeXt.  If not, see <http://www.gnu.org/licenses/>.
     <xsl:apply-templates select="$publisher-attribute-options/revealjs/appearance/pi:pub-attribute[@name='theme']" mode="set-pubfile-variable"/>
 </xsl:variable>
 
+<!-- A space-separated list of CSS URLs (points to servers or local files) -->
+<xsl:variable name="reveal-custom-css">
+    <xsl:apply-templates select="$publisher-attribute-options/revealjs/appearance/pi:pub-attribute[@name='custom-css']" mode="set-pubfile-variable"/>
+</xsl:variable>
+
 <!-- Reveal.js Controls Back Arrows -->
 
 <xsl:variable name="reveal-control-backarrow">
@@ -3236,6 +3241,7 @@ along with PreTeXt.  If not, see <http://www.gnu.org/licenses/>.
     <revealjs>
         <appearance>
             <pi:pub-attribute name="theme" default="simple" freeform="yes"/>
+            <pi:pub-attribute name="custom-css" default="" freeform="yes"/>
         </appearance>
         <controls>
             <pi:pub-attribute name="backarrows" default="faded" options="hidden visible"/>