optimize CSS to make the selection of blocks more intuitive

src/main/frontend/components/block.css

@@ -365,6 +365,10 @@
   }
 }
 
+.block-main-container {
+  padding: 2px 0;
+}
+
 .ls-block {
   position: relative;
   min-height: 24px;
@@ -372,12 +376,21 @@
   border-bottom: 1px solid transparent;
   transition: background-color 0.3s cubic-bezier(0.16, 1, 0.3, 1);
 
-  &.selected {
-    border-bottom-color: var(--ls-primary-background-color);
-    border-radius: 2px;
+  &[haschild="true"] {
+    &.selected {
+      > .block-main-container {
+        border-bottom-width: 1px;
+        border-bottom-style: solid;
+        border-bottom-color: var(--ts-primary-background-cotor);
+        border-radius: 2px;
+      }
+    }
+  }
 
-    &:last-child {
-      border-bottom-color: transparent;
+  &[haschild="false"] {
+    &.selected {
+      border-bottom-color: var(--ts-primary-background-cotor);
+      border-radius: 2px;
     }
   }
 }