diff --git a/src/processor/gpu.rs b/src/processor/gpu.rs
index b4549cb..0ad6ca0 100644
--- a/src/processor/gpu.rs
+++ b/src/processor/gpu.rs
@@ -5,7 +5,7 @@ use self::{
     },
 };
 use crate::{
-    processor::{get_bit, set_bit, set_or_clear_bit, CPU},
+    processor::{clear_bit, get_bit, set_bit, set_or_clear_bit, CPU},
     FACTOR, HEIGHT, WIDTH,
 };
 use minifb::{Window, WindowOptions};
@@ -182,6 +182,9 @@ impl CPU {
             || (mode_0_hblank_enabled && mode_0_hblank)
         {
             self.memory.set(0xFF0F, set_bit(self.memory.get(0xFF0F), 1));
+        } else {
+            self.memory
+                .set(0xFF0F, clear_bit(self.memory.get(0xFF0F), 1));
         }
 
         stat = set_or_clear_bit(stat, 2, lyc_eq_ly);
@@ -200,6 +203,9 @@ impl CPU {
     }
 
     fn render_scanline(&mut self, scanline: u8, lcdc: &LCDC) {
+        for x in 0..WIDTH {
+            self.gpu.buffer[(scanline as usize * WIDTH) + x] = Colour::from_u8_rgb(255, 0, 255);
+        }
         let bg_palette = byte_to_palette(self.memory.get(0xFF47));
         if lcdc.bg_window_enable {
             self.render_scanline_bg(scanline, lcdc, bg_palette);
@@ -218,8 +224,8 @@ impl CPU {
     }
 
     fn render_scanline_bg(&mut self, scanline: u8, lcdc: &LCDC, palette: Palette) {
-        let scroll_y = self.memory.get(0xFF42);
-        let scroll_x = self.memory.get(0xFF43);
+        let scroll_y = 0_u8.wrapping_sub(self.memory.get(0xFF42));
+        let scroll_x = 0_u8.wrapping_sub(self.memory.get(0xFF43));
         self.render_tiles(
             scanline,
             &lcdc.bg_tilemap,
@@ -333,8 +339,8 @@ impl CPU {
         offset_y: u8,
         wrap: bool,
     ) {
-        let tile_line_y = scanline.wrapping_add(offset_y);
-        if ((scanline as usize + offset_y as usize) / 0xFF) > 0 && !wrap {
+        let (tile_line_y, did_wrap_y) = scanline.overflowing_sub(offset_y);
+        if did_wrap_y && !wrap {
             return;
         }
         let tilemap_row = tile_line_y / 8;
@@ -342,8 +348,8 @@ impl CPU {
         let tiledata_offset = tile_px_y * 2;
         let row_addr = ((tilemap_row as usize * 32) % 0x400) as u16;
         for x in 0..WIDTH {
-            let tile_line_x = (x as u8).wrapping_add(offset_x);
-            if ((x + offset_x as usize) / 0xFF) > 0 && !wrap {
+            let (tile_line_x, did_wrap_x) = (x as u8).overflowing_sub(offset_x);
+            if did_wrap_x && !wrap {
                 continue;
             }
 
diff --git a/src/processor/gpu/types.rs b/src/processor/gpu/types.rs
index 575f9bc..5c113bb 100644
--- a/src/processor/gpu/types.rs
+++ b/src/processor/gpu/types.rs
@@ -1,6 +1,6 @@
 use crate::processor::as_signed;
 
-#[derive(PartialEq)]
+#[derive(Debug, PartialEq, Clone, Copy)]
 pub(super) enum DrawMode {
     HBlank,
     VBlank,
@@ -8,7 +8,7 @@ pub(super) enum DrawMode {
     Mode3,
 }
 
-#[derive(Debug)]
+#[derive(Debug, PartialEq, Clone, Copy)]
 pub(super) enum TilemapArea {
     T9800,
     T9C00,
@@ -23,7 +23,7 @@ impl TilemapArea {
     }
 }
 
-#[derive(Debug)]
+#[derive(Debug, PartialEq, Clone, Copy)]
 pub(super) enum TiledataArea {
     D8000,
     D9000,
@@ -38,7 +38,7 @@ impl TiledataArea {
     }
 }
 
-#[derive(Debug, PartialEq)]
+#[derive(Debug, PartialEq, Clone, Copy)]
 pub(super) enum ObjSize {
     S8x8,
     S8x16,
@@ -53,7 +53,7 @@ impl ObjSize {
     }
 }
 
-#[derive(Debug)]
+#[derive(Debug, PartialEq, Clone, Copy)]
 pub(super) struct LCDC {
     pub(super) enable: bool,
     pub(super) window_tilemap: TilemapArea,