diff --git a/renderer/Background.ts b/renderer/Background.ts
index f943f33..ee83994 100644
--- a/renderer/Background.ts
+++ b/renderer/Background.ts
@@ -96,6 +96,7 @@ export async function generateBg(
   map: string[][],
   cellSize = 64,
 ): Promise<HTMLImageElement> {
+  const tileSize = 64;
   const floor = assets.floor;
   const tileMap = assets.tileMap;
 
@@ -117,6 +118,10 @@ export async function generateBg(
 
   for (let y = 0; y < map.length; y++) {
     for (let x = 0; x < map[y].length; x++) {
+      if (map[y][x] !== "R") {
+        continue;
+      }
+
       const bitMask = getBitMask(map, x, y);
       const tileIdx = BITMASK_TO_TILE_INDEX[bitMask];
 
@@ -129,10 +134,10 @@ export async function generateBg(
 
       ctx.drawImage(
         tileMap,
-        sy * 64,
-        sx * 64,
-        64,
-        64,
+        sx * tileSize,
+        sy * tileSize,
+        tileSize,
+        tileSize,
         x * cellSize,
         y * cellSize,
         cellSize,