split css style into layers for explicit per-site styling

assets/css/style.css

@@ -1,62 +1,70 @@
-:root {
+@layer base, per-site;
+
+@layer base {
+  :root {
     /* Use a shade of the c3cat logos pink, which works nicely as a link color. */
     --accent-color-light: #DC049B;
     /* A modified version of accent-color-light, which works nicely as a link color
      * and with the dark theme */
     --accent-color-dark: #dc49b0;
-}
+  }
 
-body {
+  body {
     font-family: system-ui,"Segoe UI",Roboto,Oxygen,Ubuntu,Cantarell,Helvetica,Arial,"Helvetica Neue",sans-serif;
 
     text-align: left;
 
     /* Use dark grey instead of black to be lighter on the eyes. But also a grey
      * which still works with the link color nicely. */
-  background-color: #ffffff;
+    --bg-color: #ffffff;
-  color: #2B2B2B;
+    --fg-color: #2b2b2b;
+    --accent-color: var(--accent-color-light);
+    background-color: var(--bg-color);
+    color: var(--fg-color);
 
     @media (prefers-color-scheme: dark) {
       /* Colors for dark theme, which have enough contrast, but also aren't too harsh on the eyes. */
       /* See: https://seirdy.one/posts/2020/11/23/website-best-practices/#dark-themes */
-    background-color: #1b1b1b;
+      --bg-color: #1b1b1b;
-    color: #ebebeb;
+      --fg-color: #ebebeb;
+      --accent-color: var(--accent-color-dark);
+    }
   }
-}
 
-.container {
+  .container {
     max-width: 600px;
     margin: 0 auto;
     padding: 0 5px;
-}
-
-footer {
-  margin-top: 4rem;
-}
-
-img {
-  width: 100%;
-}
-
-
-a:link, a:visited {
-  color: var(--accent-color-light);
-  @media (prefers-color-scheme: dark) {
-    color: var(--accent-color-dark);
   }
-}
 
+  footer {
+    margin-top: 4rem;
+  }
 
-.title {
+  img {
+    width: 100%;
+  }
+
+  a:link, a:visited {
+    color: var(--accent-color);
+  }
+
+  u {
+    text-decoration-color: var(--accent-color);
+  }
+
+  .title {
     text-align: center;
-}
+  }
 
-.hero-img {
+  .hero-img {
     max-width: 500px;
     display: block;
     margin: 0 auto;
-}
+  }
 
-p.bigger {
+  p.bigger {
     font-size: 1.2rem;
+  }
+
 }