feat(layout): use native browser scroll for game board on desktop

src/App.vue

@@ -186,7 +186,7 @@ onUnmounted(() => {
 .game-container {
   display: flex;
   flex-direction: column;
-  align-items: center;
+  align-items: stretch; /* was center */
   gap: 20px;
   width: 100%;
   padding-bottom: 50px;
@@ -202,7 +202,7 @@ onUnmounted(() => {
   align-items: center;
   width: 90%;
   max-width: 600px;
-  margin-bottom: 20px;
+  margin: 0 auto 20px auto; /* Center it manually */
   box-shadow: var(--banner-shadow);
 }
 
@@ -227,19 +227,26 @@ onUnmounted(() => {
 .game-layout {
   display: flex;
   flex-direction: column;
-  align-items: center;
+  align-items: stretch;
   gap: 20px;
   width: 100%;
-  max-width: 1200px;
   padding: 0 20px;
 }
 
-.board-section {
-  display: flex;
-  justify-content: center;
+/* Center children (except board section which handles itself) */
+.game-layout > *:not(.board-section) {
+    margin-left: auto;
+    margin-right: auto;
+    max-width: 1200px; /* Keep constraint for panels */
     width: 100%;
 }
 
+.board-section {
+  display: block;
+  width: 100%;
+  overflow-x: visible;
+}
+
 .fade-enter-active,
 .fade-leave-active {
   transition: opacity 0.3s ease;

src/components/GameBoard.vue

@@ -118,6 +118,8 @@ const computeCellSize = () => {
   const gap = parseFloat(gapRaw);
   const gridPad = parseFloat(gridPadRaw);
 
+  const isDesktop = window.matchMedia('(min-width: 769px)').matches;
+
   let containerWidth;
   if (scrollWrapper.value) {
     containerWidth = scrollWrapper.value.clientWidth;
@@ -131,8 +133,15 @@ const computeCellSize = () => {
   const availableForGrid = Math.max(0, containerWidth - hintWidth);
   
   const size = Math.floor((availableForGrid - gridPad * 2 - (store.size - 1) * gap) / store.size);
+  
+  if (isDesktop) {
+      // Desktop: Allow overflow, use comfortable size
+      cellSize.value = 30;
+  } else {
+      // Mobile: Fit to screen
       // Keep min 18, max 36
       cellSize.value = Math.max(18, Math.min(36, size));
+  }
 };
 
 const handleGlobalMouseUp = () => {
@@ -258,8 +267,15 @@ watch(() => store.size, async () => {
 /* Desktop: Remove scroll behavior to ensure full grid visibility */
 @media (min-width: 769px) {
   .game-board-wrapper {
-    overflow-x: auto; /* Allow scrolling if grid is too large (e.g. 80x80) */
-    align-items: center; /* Center the grid on desktop */
+    overflow: visible;
+    width: max-content;
+    min-width: 100%;
+    margin: 0 auto; /* Center the wrapper safely */
+    align-items: flex-start; /* Prevent cropping when centered */
+  }
+  
+  .game-container {
+      /* margin: 0 auto; - wrapper handles centering now */
   }
 }