3 files changed, 60 insertions, 50 deletions
diff --git a/public/css/layout/grid.css b/public/css/layout/grid.css
index a4fb251..25cdd95 100644
--- a/public/css/layout/grid.css
+++ b/public/css/layout/grid.css
@@ -11,12 +11,14 @@
   width: var(--grid-column-width);
 }
 
+/* On screens narrower than 16rem, there is only one column. */
+
 .grid-span-2 {
-  width: calc(var(--grid-column-width) * 2 + var(--grid-gutter-width));
+  width: var(--grid-column-width);
 }
 
 .grid-span-3 {
-  width: calc(var(--grid-column-width) * 3 + var(--grid-gutter-width) * 2);
+  width: var(--grid-column-width);
 }
 
 .width-prose {
@@ -26,51 +28,3 @@
 .grid-span-full {
   width: var(--grid-total-width);
 }
-
-.grid-span-1.grid-end {
-  margin-inline-start: calc(
-    var(--grid-column-width) * (var(--grid-column-count) - 1) +
-    var(--grid-gutter-width) * (var(--grid-column-count) - 1)
-  );
-  margin-inline-end: 0;
-}
-
-.grid-span-2.grid-end {
-  margin-inline-start: calc(
-    var(--grid-column-width) * (var(--grid-column-count) - 2) +
-    var(--grid-gutter-width) * (var(--grid-column-count) - 2)
-  );
-  margin-inline-end: 0;
-}
-
-.grid-span-3.grid-end {
-  margin-inline-start: calc(
-    var(--grid-column-width) * (var(--grid-column-count) - 3) +
-    var(--grid-gutter-width) * (var(--grid-column-count) - 3)
-  );
-  margin-inline-end: 0;
-}
-
-.grid-span-1.grid-prose-end {
-  margin-inline-start: calc(
-    var(--grid-column-width) * (var(--grid-prose-column-count) - 1) +
-    var(--grid-gutter-width) * (var(--grid-prose-column-count) - 1)
-  );
-  margin-inline-end: 0;
-}
-
-.grid-span-2.grid-prose-end {
-  margin-inline-start: calc(
-    var(--grid-column-width) * (var(--grid-prose-column-count) - 2) +
-    var(--grid-gutter-width) * (var(--grid-prose-column-count) - 2)
-  );
-  margin-inline-end: 0;
-}
-
-.grid-span-3.grid-prose-end {
-  margin-inline-start: calc(
-    var(--grid-column-width) * (var(--grid-prose-column-count) - 3) +
-    var(--grid-gutter-width) * (var(--grid-prose-column-count) - 3)
-  );
-  margin-inline-end: 0;
-}
-\ No newline at end of file
diff --git a/public/css/layout/grid.xs.css b/public/css/layout/grid.xs.css
new file mode 100644
index 0000000..e7c6d1a
--- /dev/null
+++ b/public/css/layout/grid.xs.css
@@ -0,0 +1,55 @@
+.grid-span-2 {
+  width: calc(var(--grid-column-width) * 2 + var(--grid-gutter-width));
+}
+
+.grid-span-3 {
+  width: calc(var(--grid-column-width) * 3 + var(--grid-gutter-width) * 2);
+}
+
+.grid-span-1.grid-end {
+  margin-inline-start: calc(
+    var(--grid-column-width) * (var(--grid-column-count) - 1) +
+    var(--grid-gutter-width) * (var(--grid-column-count) - 1)
+  );
+  margin-inline-end: 0;
+}
+
+.grid-span-2.grid-end {
+  margin-inline-start: calc(
+    var(--grid-column-width) * (var(--grid-column-count) - 2) +
+    var(--grid-gutter-width) * (var(--grid-column-count) - 2)
+  );
+  margin-inline-end: 0;
+}
+
+.grid-span-3.grid-end {
+  margin-inline-start: calc(
+    var(--grid-column-width) * (var(--grid-column-count) - 3) +
+    var(--grid-gutter-width) * (var(--grid-column-count) - 3)
+  );
+  margin-inline-end: 0;
+}
+
+.grid-span-1.grid-prose-end {
+  margin-inline-start: calc(
+    var(--grid-column-width) * (var(--grid-prose-column-count) - 1) +
+    var(--grid-gutter-width) * (var(--grid-prose-column-count) - 1)
+  );
+  margin-inline-end: 0;
+}
+
+.grid-span-2.grid-prose-end {
+  margin-inline-start: calc(
+    var(--grid-column-width) * (var(--grid-prose-column-count) - 2) +
+    var(--grid-gutter-width) * (var(--grid-prose-column-count) - 2)
+  );
+  margin-inline-end: 0;
+}
+
+.grid-span-3.grid-prose-end {
+  margin-inline-start: calc(
+    var(--grid-column-width) * (var(--grid-prose-column-count) - 3) +
+    var(--grid-gutter-width) * (var(--grid-prose-column-count) - 3)
+  );
+  margin-inline-end: 0;
+}
+\ No newline at end of file
diff --git a/public/css/layout/index.css b/public/css/layout/index.css
index 0d378e0..0bede83 100644
--- a/public/css/layout/index.css
+++ b/public/css/layout/index.css
@@ -1,3 +1,4 @@
 @import './grid.css';
+@import './grid.xs.css' (min-width: 16rem);
 @import './grid.md.css' (min-width: 48rem);
 @import './section-margins.css';
 \ No newline at end of file