diff --git a/gbscreen.cpp b/gbscreen.cpp
index e66570b..277b654 100644
--- a/gbscreen.cpp
+++ b/gbscreen.cpp
@@ -135,6 +135,10 @@ namespace gbscreen
     void fill_line_buffer_bkg(uint8_t LY)
     {
         const uint8_t LCDC = mem::readMem(0xff40);
+        if ((LCDC & 0x1) == 0) {
+            for (int i=0; i<160; ++i) line_buffer[i]=0;
+            return;
+        }
         const uint8_t SCY = mem::readMem(0xff42);
         const uint8_t SCX = mem::readMem(0xff43);
         const uint8_t BGP = mem::readMem(0xff47);
@@ -169,6 +173,45 @@ namespace gbscreen
         }
     }
 
+    void fill_line_buffer_win(uint8_t LY)
+    {
+        const uint8_t LCDC = mem::readMem(0xff40);
+        if ((LCDC & 0x21) == 0) return;
+        const uint8_t WY = mem::readMem(0xff4a);
+        if (LY<WY) return;
+        const uint8_t WX = mem::readMem(0xff4b);
+        const uint8_t BGP = mem::readMem(0xff47);
+        const uint16_t ty = uint8_t(LY-WY) >> 3;
+        const uint8_t ly = uint8_t(LY-WY) & 0x7;
+        uint8_t ox = WX<7 ? 7-WX : 0;
+        uint16_t tx = 0;
+
+        uint16_t base_tilemap_address = LCDC&0x40 ? 0x9c00 : 0x9800;
+
+        int pi = WX<7 ? 0 : WX-7;
+        while(true) {
+            uint16_t tilemap_address = base_tilemap_address + tx + (ty<<5);
+            uint16_t tile = mem::readMem(tilemap_address);
+            uint16_t base_tile_address = 0x8000;
+            if ( ((LCDC&0x10)==0) && (tile<128) ) base_tile_address = 0x9000;
+            uint16_t tile_address = base_tile_address + (tile<<4) + (ly*2);
+
+            uint8_t a = mem::readMem(tile_address);
+            uint8_t b = mem::readMem(tile_address+1);
+            for (int i=0; i<8; ++i) {
+                if (ox==0) {
+                    uint8_t index = (a&0x80 ? 1 : 0) + (b&0x80 ? 2 : 0 );
+                    line_buffer[pi++] = (BGP >> (index*2)) & 0x3;
+                } else {
+                    ox--;
+                }
+                a=a<<1; b=b<<1;
+                if (pi==160) return;
+            }
+            tx = (tx+1)&0x1f;
+        }
+    }
+
     struct oam_entry_t
     {
         uint8_t y, x, tile, attr;
@@ -288,6 +331,7 @@ namespace gbscreen
                         STAT = (STAT & 0xFC) | 0x02; // Set mode 2
                         if (STAT&0x20) stat_interrupt = true;
                         fill_line_buffer_bkg(LY);
+                        fill_line_buffer_win(LY);
                         fill_line_buffer_obj(LY);
                     }
                     else if (LY==154)