diff --git a/after/syntax/css/css-line-grid-1.vim b/after/syntax/css/css-line-grid-1.vim
new file mode 100644
index 0000000..26305fb
--- /dev/null
+++ b/after/syntax/css/css-line-grid-1.vim
@@ -0,0 +1,7 @@
+" TODO: create cssLineGridProp and cssLineGridAttr
+syn match cssFontProp contained "\<line-\(grid\|snap\|slack\)"
+syn match cssFontProp contained "\<box-snap\>"
+syn match cssFontAttr contained "\<half-border\>"
+syn keyword cssFontAttr contained create
+syn match cssValueNumber contained "\d\+gd"
+syn region cssFunction contained matchgroup=cssFunctionName start="\<round\(down\|up\)\s*(" end=")" oneline keepend
diff --git a/after/syntax/html.vim b/after/syntax/html.vim
index 0e4f847..36291d2 100644
--- a/after/syntax/html.vim
+++ b/after/syntax/html.vim
@@ -34,6 +34,7 @@ syn include @htmlCss syntax/css/css-counter-styles-3.vim
 syn include @htmlCss syntax/css/css-display-3.vim
 syn include @htmlCss syntax/css/css-flexbox-1.vim
 syn include @htmlCss syntax/css/css-grid-1.vim
+syn include @htmlCss syntax/css/css-line-grid-1.vim
 syn include @htmlCss syntax/css/css-lists-3.vim
 syn include @htmlCss syntax/css/css-masking-1.vim
 syn include @htmlCss syntax/css/css-overflow-3.vim
diff --git a/test/test.css b/test/test.css
index d989cfb..780b0a6 100644
--- a/test/test.css
+++ b/test/test.css
@@ -226,6 +226,14 @@
   display: same;
 }
 
+.line-grid {
+  line-grid: create;
+  line-snap: half-border;
+  line-slack: rounddown(1em);
+  box-snap: roundup(1em);
+  display: 10gd;
+}
+
 .linebox {
   alignment-adjust: central;
   alignment-baseline: mathematical;
diff --git a/test/test.html b/test/test.html
index cfff555..b255eb4 100644
--- a/test/test.html
+++ b/test/test.html
@@ -236,6 +236,14 @@
         display: same;
       }
 
+      .line-grid {
+        line-grid: create;
+        line-snap: half-border;
+        line-slack: rounddown(1em);
+        box-snap: roundup(1em);
+        display: 10gd;
+      }
+
       .linebox {
         alignment-adjust: central;
         alignment-baseline: mathematical;