safer hero style

Author: mbostock

docs/index.html

@@ -239,25 +239,25 @@
   <script id="3" type="text/markdown">
     <style>
 
-    .observablehq:first-of-type {
+    .observablehq--cell:first-of-type {
       position: relative;
       color: var(--theme-background);
       padding-bottom: 5rem;
     }
 
-    .observablehq:first-of-type h1 {
+    .observablehq--cell:first-of-type h1 {
       color: inherit;
     }
 
-    .observablehq:first-of-type h1 + h2 {
+    .observablehq--cell:first-of-type h1 + h2 {
       color: inherit;
       font-style: normal;
       font-weight: 500;
       opacity: 0.7;
       margin-top: 1rem;
     }
 
-    .observablehq:first-of-type::before {
+    .observablehq--cell:first-of-type::before {
       content: "";
       display: block;
       position: absolute;