diff --git a/bin/src/main/java/cn/navclub/nes4j/bin/screen/Render.java b/bin/src/main/java/cn/navclub/nes4j/bin/screen/Render.java
index b90923c..89520a3 100644
--- a/bin/src/main/java/cn/navclub/nes4j/bin/screen/Render.java
+++ b/bin/src/main/java/cn/navclub/nes4j/bin/screen/Render.java
@@ -85,10 +85,8 @@ public void render(PPU ppu, Frame frame) {
 
             //Render first screen background
             renderNameTable(ppu, frame, firstNameTable, new Camera(scrollX, scrollY, 256, 240), -scrollX, -scrollY);
-            //
-            //  This does not apply to games which allow
-            // simultaneous horizontal and vertical scrolling.
-            //
+
+            //  This does not apply to games which allow simultaneous horizontal and vertical scrolling.
             if (scrollX > 0) {
                 renderNameTable(ppu,
                         frame, secondNameTable, new Camera(0, 0, scrollX, 240), 256 - scrollX, 0);
@@ -97,6 +95,7 @@ public void render(PPU ppu, Frame frame) {
                         frame, secondNameTable, new Camera(0, 0, 256, scrollY), 0, 240 - scrollY);
             }
         }
+
         //Render sprite
         if (sprite) {
             var oam = ppu.getOam();
diff --git a/document/NESDoc.pdf b/document/NESDoc.pdf
new file mode 100644
index 0000000..c7c42d1
Binary files /dev/null and b/document/NESDoc.pdf differ