feat: 视觉方向与背景图素材（章节场景图、重构 CSS、界面布局）

src/index.css

@@ -1,31 +1,21 @@
 :root {
-  font: 16px/1.6 system-ui, 'PingFang SC', 'Segoe UI', sans-serif;
-  color: #d8ccb8;
-  background: #14101e;
+  font: 16px/1.6 'Noto Sans CJK SC', 'PingFang SC', 'Microsoft YaHei', sans-serif;
+  color: #e9e7df;
+  background: #111a19;
   color-scheme: dark;
   font-synthesis: none;
   text-rendering: optimizeLegibility;
   -webkit-font-smoothing: antialiased;
-  -moz-osx-font-smoothing: grayscale;
 }
 
-body {
-  margin: 0;
-}
-
-#root {
-  min-height: 100svh;
-}
-
-h1 {
-  font-size: 28px;
-}
-
-h2 {
-  font-size: 20px;
-  margin: 0 0 4px;
-}
-
-p {
-  margin: 0 0 6px;
-}
+* { box-sizing: border-box; }
+body { margin: 0; min-width: 320px; }
+#root { min-height: 100svh; }
+button, input, textarea { font: inherit; }
+button { cursor: pointer; }
+button:disabled { opacity: .48; cursor: not-allowed; }
+:focus-visible { outline: 2px solid #dfad78; outline-offset: 3px; }
+h1, h2, p { margin-top: 0; }
+h1, h2 { font-family: 'Noto Serif CJK SC', 'Songti SC', 'STSong', serif; font-weight: 500; }
+p { margin-bottom: .65em; }
+::selection { background: #a44735; color: #fff; }