diff --git a/tonalmine/stylesheets/components.css b/tonalmine/stylesheets/components.css
index b0c2b3d..67d147c 100644
--- a/tonalmine/stylesheets/components.css
+++ b/tonalmine/stylesheets/components.css
@@ -345,16 +345,35 @@ table.progress td.done { background: color-mix(in srgb, var(--md-sys-color-prima
 table.progress td.todo { background: var(--md-sys-color-secondary-container); }
 
 /***** Tooltips (plain) *****/
-.ui-tooltip {
+/* jQuery UI also adds .ui-widget.ui-widget-content, which would win over a bare .ui-tooltip. */
+.ui-tooltip.ui-widget.ui-widget-content {
   background: var(--md-sys-color-inverse-surface);
   color: var(--md-sys-color-inverse-on-surface);
+  border: 0;
   border-radius: var(--md-sys-shape-corner-extra-small);
+  box-shadow: none;
   font: var(--md-sys-typescale-body-small);
   letter-spacing: var(--md-sys-typescale-body-small-tracking);
   padding-block: 4px;
   padding-inline: 8px;
 }
 
+/***** Tooltips (rich): calendar and Gantt issue hover cards *****/
+div.tooltip:hover span.tip {
+  inline-size: 300px;
+  background-color: var(--md-sys-color-surface-container);
+  color: var(--md-sys-color-on-surface-variant);
+  border: 0;
+  border-radius: var(--md-sys-shape-corner-medium);
+  box-shadow: var(--md-sys-elevation-level2);
+  padding-block: 12px;
+  padding-inline: 16px;
+  font: var(--md-sys-typescale-body-medium);
+  letter-spacing: var(--md-sys-typescale-body-medium-tracking);
+}
+div.tooltip span.tip strong { color: var(--md-sys-color-on-surface); font-weight: 500; }
+div.tooltip span.tip .avatar { vertical-align: middle; }
+
 /***** jQuery UI: dialogs, date picker, menus *****/
 .ui-widget, .ui-widget input, .ui-widget select, .ui-widget textarea, .ui-widget button { font-family: var(--md-ref-typeface-plain); }
 .ui-widget.ui-widget-content, .ui-widget-content {
diff --git a/tonalmine/stylesheets/typography.css b/tonalmine/stylesheets/typography.css
index f14f99c..6c94318 100644
--- a/tonalmine/stylesheets/typography.css
+++ b/tonalmine/stylesheets/typography.css
@@ -25,7 +25,7 @@ p.breadcrumb, p.subtitle, p.footnote, div.issue p.author, div.issue div.subject
 #issue_tree .issues-stat, #relations .issues-stat, .wiki-update-info, p.other-formats, em.info,
 div.attachments span.author, table.files tr.file td.digest, tr.entry td.size,
 table.plugins span.description, table.plugins span.url, #document-list .document-item .updated_on,
-.cal .calbody, div.tooltip:hover span.tip, div.issue.details .reaction, div.message .reaction, div.news .reaction {
+.cal .calbody, div.issue.details .reaction, div.message .reaction, div.news .reaction {
   font-size: 0.75rem;
 }
 div.issue span.private, div.journal span.private { font-size: 0.6875rem; }