diff --git a/apps/client/src/index.css b/apps/client/src/index.css
index 49a9f22..d257b62 100644
--- a/apps/client/src/index.css
+++ b/apps/client/src/index.css
@@ -14,6 +14,16 @@
   -moz-osx-font-smoothing: grayscale;
 }
 
+html,
+body,
+#app {
+  width: 100%;
+  height: 100%;
+  margin: 0;
+  overflow: hidden;
+  overscroll-behavior: none;
+}
+
 a {
   font-weight: 500;
   color: #646cff;
@@ -25,11 +35,7 @@
 
 /* キャンバス中央配置向け基本レイアウト */
 body {
-  margin: 0;
-  display: flex;
-  place-items: center;
   min-width: 320px;
-  min-height: 100vh;
 }
 
 h1 {
diff --git a/apps/client/src/scenes/game/styles/GameView.styles.ts b/apps/client/src/scenes/game/styles/GameView.styles.ts
index 948e134..5be6c99 100644
--- a/apps/client/src/scenes/game/styles/GameView.styles.ts
+++ b/apps/client/src/scenes/game/styles/GameView.styles.ts
@@ -8,7 +8,7 @@
 /** ゲーム画面全体のルートスタイル */
 export const GAME_VIEW_ROOT_STYLE: CSSProperties = {
   width: "100vw",
-  height: "100vh",
+  height: "100dvh",
   overflow: "hidden",
   position: "relative",
   backgroundColor: "#000",
diff --git a/apps/client/src/scenes/lobby/LobbyScene.tsx b/apps/client/src/scenes/lobby/LobbyScene.tsx
index 866d055..7a49278 100644
--- a/apps/client/src/scenes/lobby/LobbyScene.tsx
+++ b/apps/client/src/scenes/lobby/LobbyScene.tsx
@@ -102,12 +102,15 @@
       <div
         className="lobby-container"
         style={{
+          position: "fixed",
+          inset: 0,
           padding: "20px",
           color: "white",
           // 🌟 変更：元の "#222" (真っ黒) から "transparent" (透明) に変更！
           background: "transparent",
           height: "100dvh",
           width: "100vw",
+          overflow: "hidden",
           display: "flex",
           flexDirection: "column",
           alignItems: "center",