some updates to page loading performance and general performance.

added a ServiceWorker which caches stuff

css/main.css

@@ -8,6 +8,33 @@ body {
   background: #fff; 
 }
 
+/* Layout foundation: force the page to be full-height and use flex */
+html {
+  height: 100%;
+  box-sizing: border-box;
+}
+*, *::before, *::after { box-sizing: inherit; }
+
+body {
+  min-height: 100vh;    /* robust against percentage height issues */
+  display: flex;
+  flex-direction: column;
+  margin: 0;
+  padding: 0;
+}
+
+/* make the main content take remaining space */
+main.container {
+  flex: 1 1 auto;       /* grow and shrink as needed */
+  display: block;       /* keep existing layout inside main */
+}
+
+/* allow footer to sit at bottom (if content short) */
+footer {
+  margin-top: auto;
+}
+
+
 /* Mobile-specific adjustments */
 @media (max-width: 768px) {
   body {