diff --git a/src/page/background/background.scss b/src/page/background/background.scss
index 176b94c..82105be 100644
--- a/src/page/background/background.scss
+++ b/src/page/background/background.scss
@@ -1,12 +1,6 @@
 @use '../../style/mixins' as *;
 @use '../../style/dark-mode/dark-mode' as *;
 
-#background {
-  // chrome scrolling does not work on PC without these two
-  z-index: 0;
-  position: absolute;
-}
-
 .blob {
   position: absolute;
   left: 0;
diff --git a/src/page/main/main.scss b/src/page/main/main.scss
index 07366f7..8406d2b 100644
--- a/src/page/main/main.scss
+++ b/src/page/main/main.scss
@@ -6,6 +6,9 @@ main {
   overflow-y: scroll;
   perspective: 5px;
 
+  // chrome scrolling does not work on PC without this
+  background: rgba(0, 0, 0, 0.005);
+
   @media (hover: hover) {
     &::-webkit-scrollbar-track,
     &::-webkit-scrollbar {
diff --git a/src/page/timeline/timeline-element/timeline-element.scss b/src/page/timeline/timeline-element/timeline-element.scss
index b86f13c..0599f2c 100644
--- a/src/page/timeline/timeline-element/timeline-element.scss
+++ b/src/page/timeline/timeline-element/timeline-element.scss
@@ -23,7 +23,6 @@
 
   .line-container {
     position: relative;
-    z-index: 2;
     @include q-dependent-line-container(33%);
 
     .line {