style: 打字练习改为标准键盘提示并增加特殊字符输入说明

typing.css

@@ -170,6 +170,7 @@
   gap: 0.35rem;
 }
 .kb-key {
+  flex: 0 0 auto;
   min-width: 34px;
   height: 40px;
   padding: 0 0.4rem;
@@ -179,8 +180,14 @@
   color: var(--text);
   font-size: 0.9rem;
   font-family: var(--font-mono);
-  cursor: pointer;
+  cursor: default;
+  user-select: none;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
 }
+.kb-key.wide { min-width: 64px; }
+.kb-key.altgr { min-width: 64px; }
 .kb-key.space { flex: 1; max-width: 220px; }
 .kb-key.hint {
   border-color: var(--accent);
@@ -188,6 +195,13 @@
   color: #fff;
   font-weight: 700;
 }
+#special-hint {
+  min-height: 1.6rem;
+  margin-top: 0.75rem;
+  font-size: 0.85rem;
+  color: var(--text-muted);
+  line-height: 1.5;
+}
 .finish-box {
   text-align: center;
   padding: 2rem 0;
@@ -205,10 +219,13 @@
 }
 @media (max-width: 640px) {
   .kb-key {
-    min-width: 28px;
-    height: 38px;
-    font-size: 0.8rem;
-    padding: 0 0.25rem;
+    min-width: 20px;
+    height: 34px;
+    font-size: 0.65rem;
+    padding: 0 0.1rem;
+  }
+  .kb-key.wide, .kb-key.altgr {
+    min-width: 44px;
   }
   .kb-row { gap: 0.25rem; }
 }