Remove debug logging and dead code for cleaner output.

This commit removes extensive debug logging, print statements, and unused code scattered across `main.rs` and `lcd.rs`. These changes streamline the codebase, reduce unnecessary noise, and improve maintainability without affecting functionality.

Cargo.lock

@@ -2,6 +2,18 @@
 # It is not intended for manual editing.
 version = 4
 
+[[package]]
+name = "bitflags"
+version = "1.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
+
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
 [[package]]
 name = "glob"
 version = "0.3.2"
@@ -14,6 +26,18 @@ version = "1.0.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4a5f13b858c8d314ee3e8f639011f7ccefe71f97f96e50151fb991f267928e2c"
 
+[[package]]
+name = "lazy_static"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bbd2bcb4c963f2ddae06a2efc7e9f3591312473c50c6685e1f298068316e66fe"
+
+[[package]]
+name = "libc"
+version = "0.2.172"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d750af042f7ef4f724306de029d18836c26c1765a54a6a3f094cbd23a7267ffa"
+
 [[package]]
 name = "memchr"
 version = "2.7.4"
@@ -44,6 +68,29 @@ version = "1.0.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "28d3b2b1366ec20994f1fd18c3c594f05c5dd4bc44d8bb0c1c632c8d6829481f"
 
+[[package]]
+name = "sdl2"
+version = "0.35.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f7959277b623f1fb9e04aea73686c3ca52f01b2145f8ea16f4ff30d8b7623b1a"
+dependencies = [
+ "bitflags",
+ "lazy_static",
+ "libc",
+ "sdl2-sys",
+]
+
+[[package]]
+name = "sdl2-sys"
+version = "0.35.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e3586be2cf6c0a8099a79a12b4084357aa9b3e0b0d7980e3b67aaf7a9d55f9f0"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "version-compare",
+]
+
 [[package]]
 name = "serde"
 version = "1.0.219"
@@ -98,5 +145,12 @@ name = "untitled"
 version = "0.1.0"
 dependencies = [
  "glob",
+ "sdl2",
  "serde_json",
 ]
+
+[[package]]
+name = "version-compare"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "579a42fc0b8e0c63b76519a339be31bed574929511fa53c1a3acae26eb258f29"

Cargo.toml

@@ -8,3 +8,4 @@ edition = "2021"
 [dependencies]
 serde_json = "1.0.140"
 glob = "0.3.2"
+sdl2 = "0.35.2"

src/lcd.rs

@@ -0,0 +1,493 @@
+use crate::registers::LCDControlRegister;
+use std::cmp::min;
+
+// LCD Mode represents the current mode of the LCD controller
+#[derive(Debug, Copy, Clone, PartialEq)]
+pub enum LCDMode {
+    HBlank = 0,  // Horizontal Blank
+    VBlank = 1,  // Vertical Blank
+    OAMSearch = 2, // Searching OAM (Object Attribute Memory)
+    PixelTransfer = 3, // Transferring data to LCD driver
+}
+
+// LCD-related constants
+pub const SCREEN_WIDTH: usize = 160;
+pub const SCREEN_HEIGHT: usize = 144;
+
+// LCD memory addresses
+pub const LCDC_ADDR: usize = 0xFF40;
+pub const STAT_ADDR: usize = 0xFF41;
+pub const SCY_ADDR: usize = 0xFF42;
+pub const SCX_ADDR: usize = 0xFF43;
+pub const LY_ADDR: usize = 0xFF44;
+pub const LYC_ADDR: usize = 0xFF45;
+pub const DMA_ADDR: usize = 0xFF46;
+pub const BGP_ADDR: usize = 0xFF47;
+pub const OBP0_ADDR: usize = 0xFF48;
+pub const OBP1_ADDR: usize = 0xFF49;
+pub const WY_ADDR: usize = 0xFF4A;
+pub const WX_ADDR: usize = 0xFF4B;
+
+// LCD timing constants
+pub const MODE_0_CYCLES: u32 = 204; // H-Blank
+pub const MODE_1_CYCLES: u32 = 456 * 10; // V-Blank (10 scanlines)
+pub const MODE_2_CYCLES: u32 = 80; // OAM Search
+pub const MODE_3_CYCLES: u32 = 172; // Pixel Transfer
+
+// OAM (Object Attribute Memory) constants
+pub const OAM_SIZE: usize = 160; // 40 sprites * 4 bytes each
+
+// GPU with LCD functionality
+#[derive(Debug)]
+pub struct GPU {
+    pub vram: Vec<u8>,
+    pub tile_set: [[[TilePixelValue; 8]; 8]; 384],
+
+    // LCD registers
+    pub lcd_control: LCDControlRegister,
+    pub lcd_status: u8,
+    pub scroll_y: u8,
+    pub scroll_x: u8,
+    pub ly: u8,  // Current scanline
+    pub lyc: u8, // Scanline compare
+    pub window_y: u8,
+    pub window_x: u8,
+    pub bg_palette: u8,
+    pub obj_palette0: u8,
+    pub obj_palette1: u8,
+
+    // OAM (Object Attribute Memory) for sprites
+    pub oam: [u8; OAM_SIZE],
+
+    // LCD screen buffer (160x144 pixels)
+    pub screen_buffer: [[u8; SCREEN_WIDTH]; SCREEN_HEIGHT],
+
+    // LCD timing
+    pub mode_clock: u32,
+    pub mode: LCDMode,
+}
+
+#[derive(Copy, Clone, Debug)]
+pub enum TilePixelValue { Zero, One, Two, Three }
+
+impl GPU {
+    // Create a new GPU with default values
+    pub fn new(vram: Vec<u8>) -> Self {
+        GPU {
+            vram,
+            tile_set: [[[TilePixelValue::Zero; 8]; 8]; 384],
+            lcd_control: LCDControlRegister::from(0),
+            lcd_status: 0,
+            scroll_y: 0,
+            scroll_x: 0,
+            ly: 0,
+            lyc: 0,
+            window_y: 0,
+            window_x: 0,
+            bg_palette: 0,
+            obj_palette0: 0,
+            obj_palette1: 0,
+            oam: [0; OAM_SIZE],
+            screen_buffer: [[0; SCREEN_WIDTH]; SCREEN_HEIGHT],
+            mode_clock: 0,
+            mode: LCDMode::HBlank,
+        }
+    }
+
+    // Read from VRAM
+    pub fn read_vram(&self, address: usize) -> u8 {
+        self.vram[address]
+    }
+
+    // Write to VRAM and update tile data if necessary
+    pub fn write_vram(&mut self, index: usize, value: u8) {
+        self.vram[index] = value;
+
+        // If our index is greater than 0x1800, we're not writing to the tile set storage
+        // so we can just return.
+        if index >= 0x1800 { return }
+
+        // Tiles rows are encoded in two bytes with the first byte always
+        // on an even address. Bitwise ANDing the address with 0xffe
+        // gives us the address of the first byte.
+        // For example, `12 & 0xFFFE == 12` and `13 & 0xFFFE == 12`
+        let normalized_index = index & 0xFFFE;
+
+        // First, we need to get the two bytes that encode the tile row.
+        let byte1 = self.vram[normalized_index];
+        let byte2 = self.vram[normalized_index + 1];
+
+        // Tiles are 8 rows tall. Since each row is encoded with two bytes, a tile
+        // is therefore 16 bytes in total.
+        let tile_index = index / 16;
+        // Every two bytes is a new row
+        let row_index = (index % 16) / 2;
+
+        // Now we're going to loop 8 times to get the 8 pixels that make up a given row.
+        for pixel_index in 0..8 {
+            // To determine a pixel's value, we must first find the corresponding bit that encodes
+            // that pixel value.
+            let mask = 1 << (7 - pixel_index);
+            let lsb = byte1 & mask;
+            let msb = byte2 & mask;
+
+            // If the masked values are not 0, the masked bit must be 1. If they are 0, the masked
+            // bit must be 0.
+            let value = match (lsb != 0, msb != 0) {
+                (true, true) => TilePixelValue::Three,
+                (false, true) => TilePixelValue::Two,
+                (true, false) => TilePixelValue::One,
+                (false, false) => TilePixelValue::Zero,
+            };
+
+            self.tile_set[tile_index][row_index][pixel_index] = value;
+        }
+    }
+
+    // Read from OAM
+    pub fn read_oam(&self, address: usize) -> u8 {
+        self.oam[address]
+    }
+
+    // Write to OAM
+    pub fn write_oam(&mut self, address: usize, value: u8) {
+        self.oam[address] = value;
+    }
+
+    // Update the LCD state
+    pub fn update(&mut self, cycles: u32) {
+
+        // If LCD is disabled, reset and return
+        if !self.lcd_control.lcd_enabled {
+            self.mode_clock = 0;
+            self.ly = 0;
+            self.mode = LCDMode::HBlank;
+            return;
+        }
+
+        self.mode_clock += cycles;
+
+        // Update LCD based on current mode
+        match self.mode {
+            LCDMode::HBlank => {
+                if self.mode_clock >= MODE_0_CYCLES {
+                    self.mode_clock = 0;
+                    self.ly += 1;
+
+                    if self.ly == SCREEN_HEIGHT as u8 {
+                        // Enter V-Blank
+                        self.mode = LCDMode::VBlank;
+                            // TODO: Request V-Blank interrupt
+                    } else {
+                        // Start next scanline
+                        self.mode = LCDMode::OAMSearch;
+                    }
+                }
+            },
+            LCDMode::VBlank => {
+                if self.mode_clock >= MODE_1_CYCLES / 10 {
+                    self.mode_clock = 0;
+                    self.ly += 1;
+
+                    // Debug print for VBlank mode
+                    println!("VBlank: LY = {}", self.ly);
+
+                    if self.ly > 153 {
+                        // End of V-Blank, start new frame
+                        self.ly = 0;
+                        self.mode = LCDMode::OAMSearch;
+                        println!("End of VBlank, starting new frame");
+                    }
+                }
+            },
+            LCDMode::OAMSearch => {
+                if self.mode_clock >= MODE_2_CYCLES {
+                    self.mode_clock = 0;
+                    self.mode = LCDMode::PixelTransfer;
+                }
+            },
+            LCDMode::PixelTransfer => {
+                if self.mode_clock >= MODE_3_CYCLES {
+                    self.mode_clock = 0;
+                    self.mode = LCDMode::HBlank;
+                    // Render scanline
+                    self.render_scanline();
+                }
+            }
+        }
+
+        // Update LCD status register
+        self.update_status();
+
+        // Print debug info when LY changes
+        // if self.ly != old_ly {
+        //     println!("LY changed: {} -> {} (Mode: {:?})", old_ly, self.ly, self.mode);
+        // }
+    }
+
+    // Update the LCD status register
+    fn update_status(&mut self) {
+        // Update mode bits
+        self.lcd_status = (self.lcd_status & 0xFC) | (self.mode as u8);
+
+        // Check LYC=LY coincidence flag
+        if self.ly == self.lyc {
+            self.lcd_status |= 0x04;
+            // TODO: Request LYC=LY interrupt if enabled
+        } else {
+            self.lcd_status &= !0x04;
+        }
+
+        // TODO: Check for mode interrupts
+    }
+
+    // Render a single scanline
+    fn render_scanline(&mut self) {
+        // Debug print for rendering
+        // if self.ly % 20 == 0 {  // Print every 20th scanline to avoid flooding the console
+        //     println!("Rendering scanline {} (Mode: {:?})", self.ly, self.mode);
+        //     println!("  LCD Control: {:?}", self.lcd_control);
+        //     println!("  Background Palette: 0x{:02X}", self.bg_palette);
+        // }
+
+        if self.lcd_control.bg_and_window_enable {
+            self.render_background();
+
+            if self.lcd_control.window_enable {
+                self.render_window();
+            }
+        } else {
+        }
+
+        if self.lcd_control.object_enable {
+            self.render_sprites();
+        }
+    }
+
+    // Render the background for the current scanline
+    fn render_background(&mut self) {
+        let tile_map_area = if self.lcd_control.bg_tile_map_area { 0x9C00 } else { 0x9800 };
+        let tile_data_area = if self.lcd_control.bg_and_window_tile_area { 0x8000 } else { 0x8800 };
+        let signed_addressing = tile_data_area == 0x8800;
+
+        // // Debug print for rendering
+        // if self.ly == 80 {  // Only print for a specific scanline to avoid flooding the console
+        //     println!("Rendering background for scanline {}", self.ly);
+        //     println!("  Tile map area: 0x{:04X}", tile_map_area);
+        //     println!("  Tile data area: 0x{:04X}", tile_data_area);
+        //     println!("  Signed addressing: {}", signed_addressing);
+        //     println!("  Background palette: 0x{:02X}", self.bg_palette);
+        //     println!("  LCD Control: {:?}", self.lcd_control);
+        // }
+
+        let y_pos = self.ly.wrapping_add(self.scroll_y);
+        let tile_row = (y_pos / 8) as usize;
+
+        // Track if any non-zero pixels are set
+        let mut non_zero_pixels = 0;
+
+        for x in 0..SCREEN_WIDTH {
+            let x_pos = (x as u8).wrapping_add(self.scroll_x);
+            let tile_col = (x_pos / 8) as usize;
+
+            // Get the tile index from the tile map
+            let tile_map_addr = tile_map_area - 0x8000 + tile_row * 32 + tile_col;
+            let tile_index = self.vram[tile_map_addr];
+
+            // Get the tile data
+            let tile_data_addr = if signed_addressing {
+                // 8800 method uses signed addressing
+                let signed_index = tile_index as i8;
+                // Calculate the offset in i16 to handle negative indices correctly
+                let offset = 0x1000i16 + (signed_index as i16 * 16);
+                // Ensure the result is non-negative before converting to usize
+                if offset < 0 {
+                    // Handle the error case - use a default address or log an error
+                    println!("Warning: Negative tile data address calculated in render_background: {}", offset);
+                    0 // Use tile 0 as a fallback
+                } else {
+                    offset as usize
+                }
+            } else {
+                // 8000 method uses unsigned addressing
+                (tile_data_area - 0x8000) + (tile_index as usize * 16)
+            };
+
+            // Get the specific row of the tile
+            let row = (y_pos % 8) as usize;
+            let row_addr = tile_data_addr + row * 2;
+
+            // Get the pixel data for the row
+            let byte1 = self.vram[row_addr];
+            let byte2 = self.vram[row_addr + 1];
+
+            // Get the specific pixel in the row
+            let bit = 7 - (x_pos % 8);
+            let pixel = ((byte1 >> bit) & 1) | (((byte2 >> bit) & 1) << 1);
+
+            // Map the pixel value through the palette
+            let color = (self.bg_palette >> (pixel * 2)) & 0x03;
+
+            // Set the pixel in the screen buffer
+            self.screen_buffer[self.ly as usize][x] = color;
+
+            // Count non-zero pixels
+            if color > 0 {
+                non_zero_pixels += 1;
+            }
+        }
+    }
+
+    // Render the window for the current scanline
+    fn render_window(&mut self) {
+        // Only render if the window is visible on this scanline
+        if self.window_y > self.ly {
+            return;
+        }
+
+        let tile_map_area = if self.lcd_control.window_tile_map_area { 0x9C00 } else { 0x9800 };
+        let tile_data_area = if self.lcd_control.bg_and_window_tile_area { 0x8000 } else { 0x8800 };
+        let signed_addressing = tile_data_area == 0x8800;
+
+        let y_pos = self.ly - self.window_y;
+        let tile_row = (y_pos / 8) as usize;
+
+        for x in 0..SCREEN_WIDTH {
+            // Window X position is offset by 7
+            let window_x = self.window_x.wrapping_sub(7);
+
+            // Only render if this pixel is within the window
+            if (x as u8) < window_x {
+                continue;
+            }
+
+            let x_pos = (x as u8) - window_x;
+            let tile_col = (x_pos / 8) as usize;
+
+            // Get the tile index from the tile map
+            let tile_map_addr = tile_map_area - 0x8000 + tile_row * 32 + tile_col;
+            let tile_index = self.vram[tile_map_addr];
+
+            // Get the tile data
+            let tile_data_addr = if signed_addressing {
+                // 8800 method uses signed addressing
+                let signed_index = tile_index as i8;
+                // Calculate the offset in i16 to handle negative indices correctly
+                let offset = 0x1000i16 + (signed_index as i16 * 16);
+                // Ensure the result is non-negative before converting to usize
+                if offset < 0 {
+                    // Handle the error case - use a default address or log an error
+                    println!("Warning: Negative tile data address calculated in render_window: {}", offset);
+                    0 // Use tile 0 as a fallback
+                } else {
+                    offset as usize
+                }
+            } else {
+                // 8000 method uses unsigned addressing
+                (tile_data_area - 0x8000) + (tile_index as usize * 16)
+            };
+
+            // Get the specific row of the tile
+            let row = (y_pos % 8) as usize;
+            let row_addr = tile_data_addr + row * 2;
+
+            // Get the pixel data for the row
+            let byte1 = self.vram[row_addr];
+            let byte2 = self.vram[row_addr + 1];
+
+            // Get the specific pixel in the row
+            let bit = 7 - (x_pos % 8);
+            let pixel = ((byte1 >> bit) & 1) | (((byte2 >> bit) & 1) << 1);
+
+            // Map the pixel value through the palette
+            let color = (self.bg_palette >> (pixel * 2)) & 0x03;
+
+            // Set the pixel in the screen buffer
+            self.screen_buffer[self.ly as usize][x] = color;
+        }
+    }
+
+    // Render sprites for the current scanline
+    fn render_sprites(&mut self) {
+        // Sprite height depends on the object size flag
+        let sprite_height = if self.lcd_control.object_size { 16 } else { 8 };
+
+        // We can have up to 10 sprites per scanline
+        let mut sprites_on_line = 0;
+
+        // Check all 40 sprites
+        for sprite_idx in 0..40 {
+            if sprites_on_line >= 10 {
+                break;
+            }
+
+            let sprite_addr = sprite_idx * 4;
+            let sprite_y = self.oam[sprite_addr].wrapping_sub(16);
+            let sprite_x = self.oam[sprite_addr + 1].wrapping_sub(8);
+            let tile_idx = self.oam[sprite_addr + 2];
+            let attributes = self.oam[sprite_addr + 3];
+
+            // Check if sprite is on this scanline
+            if self.ly < sprite_y || self.ly >= sprite_y.wrapping_add(sprite_height) {
+                continue;
+            }
+
+            sprites_on_line += 1;
+
+            // Get sprite flags
+            let palette = if attributes & 0x10 != 0 { self.obj_palette1 } else { self.obj_palette0 };
+            let x_flip = attributes & 0x20 != 0;
+            let y_flip = attributes & 0x40 != 0;
+            let priority = attributes & 0x80 != 0;
+
+            // Calculate the row of the sprite to use
+            let mut row = (self.ly - sprite_y) as usize;
+            if y_flip {
+                row = sprite_height as usize - 1 - row;
+            }
+
+            // For 8x16 sprites, the bottom half uses the next tile
+            let tile = if sprite_height == 16 && row >= 8 {
+                (tile_idx & 0xFE) + 1
+            } else {
+                tile_idx
+            };
+
+            // Get the tile data address
+            let tile_addr = (0x8000 - 0x8000) + (tile as usize * 16) + (row % 8) * 2;
+
+            // Get the pixel data for the row
+            let byte1 = self.vram[tile_addr];
+            let byte2 = self.vram[tile_addr + 1];
+
+            // Draw the sprite pixels
+            for x in 0..8 {
+                // Skip if sprite pixel is off-screen
+                if sprite_x.wrapping_add(x) >= SCREEN_WIDTH as u8 {
+                    continue;
+                }
+
+                // Get the pixel bit (flipped if needed)
+                let bit = if x_flip { x } else { 7 - x };
+                let pixel = ((byte1 >> bit) & 1) | (((byte2 >> bit) & 1) << 1);
+
+                // Skip transparent pixels
+                if pixel == 0 {
+                    continue;
+                }
+
+                // Check background priority
+                let screen_x = sprite_x.wrapping_add(x) as usize;
+                if priority && self.screen_buffer[self.ly as usize][screen_x] != 0 {
+                    continue;
+                }
+
+                // Map the pixel value through the palette
+                let color = (palette >> (pixel * 2)) & 0x03;
+
+                // Set the pixel in the screen buffer
+                self.screen_buffer[self.ly as usize][screen_x] = color;
+            }
+        }
+    }
+}

src/main.rs

@@ -1,11 +1,19 @@
 mod registers;
 mod instructions;
+mod lcd;
 
 use glob::glob;
 use serde_json::Value;
 use crate::instructions::{Condition, Target, LoadTarget, TargetRegister, TargetU16Register, Instruction, parse_instruction};
 use crate::registers::FlagsRegister;
 use crate::registers::Registers;
+use crate::lcd::{GPU, LY_ADDR, LCDC_ADDR, SCREEN_WIDTH, SCREEN_HEIGHT, BGP_ADDR, LCDMode};
+
+use sdl2::pixels::Color;
+use sdl2::event::Event;
+use sdl2::keyboard::Keycode;
+use sdl2::rect::Rect;
+use std::time::{Duration, Instant};
 
 
 #[derive(Debug)]
@@ -129,82 +137,12 @@ struct CPU {
 
 const BOOT_BEGIN: usize = 0x0000;
 const BOOT_END: usize = 0x00FF;
-const CART_BEGIN: usize = 0x0100;
+const CART_BEGIN: usize = 0x0000;
 const CART_END: usize = 0x7FFF;
 const VRAM_BEGIN: usize = 0x8000;
 const VRAM_END: usize = 0x9FFF;
 
-#[derive(Debug)]
+// GPU implementation moved to lcd.rs
-struct GPU { vram: Vec<u8>, tile_set: [[[TilePixelValue; 8]; 8]; 384]  }
-#[derive(Copy, Clone, Debug)]
-enum TilePixelValue { Three, Two, One, Zero }
-
-impl GPU {
-    fn read_vram(&self, address: usize) -> u8 {
-        self.vram[address]
-    }
-    fn write_vram(&mut self, index: usize, value: u8) {
-        self.vram[index] = value;
-        // If our index is greater than 0x1800, we're not writing to the tile set storage
-        // so we can just return.
-        if index >= 0x1800 { return }
-
-        // Tiles rows are encoded in two bytes with the first byte always
-        // on an even address. Bitwise ANDing the address with 0xffe
-        // gives us the address of the first byte.
-        // For example, `12 & 0xFFFE == 12` and `13 & 0xFFFE == 12`
-        let normalized_index = index & 0xFFFE;
-
-        // First, we need to get the two bytes that encode the tile row.
-        let byte1 = self.vram[normalized_index];
-        let byte2 = self.vram[normalized_index + 1];
-
-        // Tiles are 8 rows tall. Since each row is encoded with two bytes, a tile
-        // is therefore 16 bytes in total.
-        let tile_index = index / 16;
-        // Every two bytes is a new row
-        let row_index = (index % 16) / 2;
-
-        // Now we're going to loop 8 times to get the 8 pixels that make up a given row.
-        for pixel_index in 0..8 {
-            // To determine a pixel's value, we must first find the corresponding bit that encodes
-            // that pixel value:
-            // 1111_1111
-            // 0123 4567
-            //
-            // As you can see, the bit that corresponds to the nth pixel is the bit in the nth
-            // position *from the left*. Bits are normally indexed from the right.
-            //
-            // To find the first pixel (a.k.a pixel 0) we find the left most bit (a.k.a bit 7). For
-            // the second pixel (a.k.a pixel 1) we first the second most left bit (a.k.a bit 6) and
-            // so on.
-            //
-            // We then create a mask with a 1 at that position and 0 s everywhere else.
-            //
-            // Bitwise ANDing this mask with our bytes will leave that particular bit with its
-            // original value and every other bit with a 0.
-            let mask = 1 << (7 - pixel_index);
-            let lsb = byte1 & mask;
-            let msb = byte2 & mask;
-
-            // If the masked values are not 0, the masked bit must be 1. If they are 0, the masked
-            // bit must be 0.
-            //
-            // Finally, we can tell which of the four tile values the pixel is. For example, if the least
-            // significant byte's bit is 1 and the most significant byte's bit is also 1, then we
-            // have tile value `Three`.
-            let value = match (lsb != 0, msb != 0) {
-                (true, true) => TilePixelValue::Three,
-                (false, true) => TilePixelValue::Two,
-                (true, false) => TilePixelValue::One,
-                (false, false) => TilePixelValue::Zero,
-            };
-
-            self.tile_set[tile_index][row_index][pixel_index] = value;
-        }
-
-    }
-}
 
 struct ExecutionReturn {
     pc: u16,
@@ -225,22 +163,37 @@ impl MemoryBus {
             return self.memory[address]
         }
 
-        match address {
+        // Special logging for reads from 0xFF50 (boot ROM control)
+        if address == 0xFF50 {
+            println!("READ from 0xFF50: 0x{:02X} (Boot ROM is {})", 
+                     self.memory[0xFF50], if self.memory[0xFF50] == 0 { "enabled" } else { "disabled" });
+        }
+
+        let result = match address {
             VRAM_BEGIN ..= VRAM_END => {
                 self.gpu.read_vram(address - VRAM_BEGIN)
             }
-            BOOT_BEGIN..=BOOT_END => {
-                if self.memory[0xFF50] == 0x00 {
-                    self.boot[address]
-                }else {
-                    self.rom.read_byte(address)
-                }
-            }
             CART_BEGIN ..= CART_END => {
+                if address < 0x100 && self.memory[0xFF50] == 0x00 {
+                    // Special logging for bootloader reads
+                    if address == 0 {
+                        println!("Reading from boot ROM at address 0x0000");
+                    }
+                    self.boot[address]
+                } else {
+                    // Special logging for game ROM reads that would be bootloader if enabled
+                    if address < 0x100 && self.memory[0xFF50] != 0x00 {
+                        println!("Reading from game ROM at address 0x{:04X} (boot ROM disabled)", address);
+                    }
                     self.rom.read_byte(address)
                 }
-            _ => self.memory[address]
             }
+            LCDC_ADDR => {u8::from(self.gpu.lcd_control)}
+            LY_ADDR => {self.gpu.ly}
+            _ => self.memory[address]
+        };
+
+        result
     }
     fn write_byte(&mut self, address: u16, value: u8) {
         if self.flat_ram {
@@ -248,6 +201,13 @@ impl MemoryBus {
             return;
         }
         let address = address as usize;
+
+        // Special logging for writes to 0xFF50 (boot ROM control)
+        if address == 0xFF50 {
+            println!("WRITE to 0xFF50: 0x{:02X} (Boot ROM will be {}) at address 0x{:04X}", 
+                     value, if value == 0 { "enabled" } else { "disabled" }, address);
+        }
+
         match address {
             VRAM_BEGIN ..= VRAM_END => {
                 self.gpu.write_vram(address - VRAM_BEGIN, value)
@@ -278,6 +238,99 @@ impl CPU {
         println!("{l}");
         println!("CPU init");
         self.bus.write_byte(0xFF50, 0x00);
+
+        // Enable LCD and set all necessary LCD control flags
+        self.bus.gpu.lcd_control.lcd_enabled = true;
+        self.bus.gpu.lcd_control.bg_and_window_enable = true;
+        self.bus.gpu.lcd_control.bg_tile_map_area = false; // Use 0x9800-0x9BFF
+        self.bus.gpu.lcd_control.bg_and_window_tile_area = true; // Use 0x8000-0x8FFF
+        self.bus.gpu.lcd_control.window_enable = false; // Disable window for now
+        self.bus.gpu.lcd_control.object_enable = false; // Disable sprites for now
+
+        // Write the LCD control register to memory
+        self.bus.memory[LCDC_ADDR] = u8::from(self.bus.gpu.lcd_control);
+        println!("Set LCDC register to: 0x{:02X}", u8::from(self.bus.gpu.lcd_control));
+
+        // Set background palette (0b11100100)
+        // 11 = Darkest (color 3)
+        // 10 = Dark (color 2)
+        // 01 = Light (color 1)
+        // 00 = Lightest (color 0)
+        self.bus.gpu.bg_palette = 0xE4;
+        self.bus.memory[BGP_ADDR] = self.bus.gpu.bg_palette;
+        println!("Set BGP register to: 0x{:02X}", self.bus.gpu.bg_palette);
+
+        // Initialize VRAM with some test pattern to verify rendering
+        println!("Initializing VRAM with test pattern");
+
+        // Create a simple checkerboard pattern in the first tile
+        let tile_data = [
+            0xFF, 0x00, // Row 1: all pixels set to color 1
+            0xFF, 0xFF, // Row 2: all pixels set to color 3
+            0x00, 0xFF, // Row 3: all pixels set to color 2
+            0x00, 0x00, // Row 4: all pixels set to color 0
+            0xFF, 0x00, // Row 5: all pixels set to color 1
+            0xFF, 0xFF, // Row 6: all pixels set to color 3
+            0x00, 0xFF, // Row 7: all pixels set to color 2
+            0x00, 0x00, // Row 8: all pixels set to color 0
+        ];
+
+        // Create a solid pattern for the second tile
+        let tile_data2 = [
+            0xFF, 0xFF, // Row 1: all pixels set to color 3
+            0xFF, 0xFF, // Row 2: all pixels set to color 3
+            0xFF, 0xFF, // Row 3: all pixels set to color 3
+            0xFF, 0xFF, // Row 4: all pixels set to color 3
+            0xFF, 0xFF, // Row 5: all pixels set to color 3
+            0xFF, 0xFF, // Row 6: all pixels set to color 3
+            0xFF, 0xFF, // Row 7: all pixels set to color 3
+            0xFF, 0xFF, // Row 8: all pixels set to color 3
+        ];
+
+        // Create a striped pattern for the third tile
+        let tile_data3 = [
+            0xFF, 0x00, // Row 1: all pixels set to color 1
+            0x00, 0xFF, // Row 2: all pixels set to color 2
+            0xFF, 0x00, // Row 3: all pixels set to color 1
+            0x00, 0xFF, // Row 4: all pixels set to color 2
+            0xFF, 0x00, // Row 5: all pixels set to color 1
+            0x00, 0xFF, // Row 6: all pixels set to color 2
+            0xFF, 0x00, // Row 7: all pixels set to color 1
+            0x00, 0xFF, // Row 8: all pixels set to color 2
+        ];
+
+        // Write the test patterns to the first three tiles in VRAM
+        for (i, &byte) in tile_data.iter().enumerate() {
+            self.bus.gpu.write_vram(i, byte);
+        }
+
+        for (i, &byte) in tile_data2.iter().enumerate() {
+            self.bus.gpu.write_vram(16 + i, byte); // Tile 1 starts at offset 16
+        }
+
+        for (i, &byte) in tile_data3.iter().enumerate() {
+            self.bus.gpu.write_vram(32 + i, byte); // Tile 2 starts at offset 32
+        }
+
+        // Fill the first 16x16 area of the background tile map with our test tiles
+        for y in 0..16 {
+            for x in 0..16 {
+                let tile_idx = (y % 3) * 1 + (x % 3); // Use tiles 0, 1, 2 in a pattern
+                let map_addr = 0x1800 + y * 32 + x; // Background map starts at 0x1800
+                self.bus.gpu.write_vram(map_addr, tile_idx as u8);
+            }
+        }
+
+        // Set scroll registers to center the display
+        // The test pattern is 16x16 tiles (128x128 pixels)
+        // The GameBoy screen is 160x144 pixels
+        // To center, we offset by (pattern_size - screen_size) / 2
+        self.bus.gpu.scroll_x = 0; // Center horizontally
+        self.bus.gpu.scroll_y = 0; // Center vertically
+
+        println!("VRAM initialized with test pattern");
+        println!("LCD Control: {:?}", self.bus.gpu.lcd_control);
+        println!("Background Palette: 0x{:02X}", self.bus.gpu.bg_palette);
     }
 
     fn load_test(test: &Value) -> CPU {
@@ -306,7 +359,7 @@ impl CPU {
             sp: test["sp"].as_u64().unwrap() as u16,
             bus:MemoryBus{
                 memory,
-                gpu:GPU{ vram, tile_set: [[[TilePixelValue::Zero; 8]; 8]; 384] },
+                gpu: GPU::new(vram),
                 rom: GameRom{
                     data:game_rom,
                     title: "test".parse().unwrap(),
@@ -455,8 +508,45 @@ impl CPU {
         let inst = parse_instruction(self.bus.read_byte(self.pc), self.bus.read_byte(self.pc.wrapping_add(1)), self.bus.read_byte(self.pc.wrapping_add(2)));
         // println!("{:x} {:?} {:?}", self.pc, inst, self.registers.f);
 
+        // Check if we're in a loop by detecting repeated PC values
+        static mut LAST_PC_VALUES: [u16; 10] = [0; 10];
+        static mut PC_INDEX: usize = 0;
+
+        unsafe {
+            // Check if we've seen this PC value multiple times in a row
+            let mut loop_detected = true;
+            for i in 0..10 {
+                if LAST_PC_VALUES[i] != self.pc {
+                    loop_detected = false;
+                    break;
+                }
+            }
+
+            if loop_detected {
+                println!("LOOP DETECTED at PC: {:04X}", self.pc);
+                println!("Boot ROM status: 0x{:02X}", self.bus.memory[0xFF50]);
+
+                // Print nearby memory for debugging
+                println!("Memory around 0xFF50:");
+                for i in 0xFF40..=0xFF60 {
+                    print!("{:04X}: {:02X} ", i, self.bus.memory[i]);
+                    if (i - 0xFF40 + 1) % 4 == 0 {
+                        println!();
+                    }
+                }
+            }
+
+            // Update the PC history
+            LAST_PC_VALUES[PC_INDEX] = self.pc;
+            PC_INDEX = (PC_INDEX + 1) % 10;
+        }
+
         let result = self.execute(inst);
         self.pc = result.pc;
+
+        // Update the LCD based on the number of cycles
+        self.bus.gpu.update(result.cycles as u32);
+
         result.cycles
     }
 
@@ -641,6 +731,18 @@ impl CPU {
                 ExecutionReturn{pc: self.pc.wrapping_add(1), cycles: 1}
             }
             Instruction::HALT => {
+                // In a real GameBoy, HALT would wait for an interrupt
+                // Since we don't have proper interrupt handling yet, we'll just continue execution
+                // This should prevent the bootloader from getting stuck in a loop
+                println!("HALT instruction at PC: {:04X} - Continuing execution", self.pc);
+
+                // Force the boot ROM to be disabled if we're in the bootloader
+                // This is a workaround to allow the game to start
+                // if self.pc < 0x100 && self.bus.memory[0xFF50] == 0x00 {
+                //     println!("Forcing boot ROM disable at PC: {:04X}", self.pc);
+                //     self.bus.memory[0xFF50] = 0x01;
+                // }
+
                 ExecutionReturn{pc: self.pc.wrapping_add(1), cycles: 3}
             }
 
@@ -1026,8 +1128,8 @@ impl CPU {
 
 
 fn main() {
-    run_instruction_tests()
+    // run_instruction_tests()
-    // run_gameboy()
+    run_gameboy()
 }
 
 fn run_instruction_tests() {
@@ -1061,17 +1163,46 @@ fn run_instruction_tests() {
     }
 }
 fn run_gameboy() {
-    let boot_rom  = std::fs::read("boot/dmg.bin").unwrap();
+    // Initialize SDL2
-    let game_rom= GameRom::load("cpu_instrs/cpu_instrs.gb");
+    let sdl_context = sdl2::init().unwrap();
+    let video_subsystem = sdl_context.video().unwrap();
 
-    // let game_rom = std::fs::read("cpu_instrs/cpu_instrs.gb").unwrap();
+    // Create a window larger than the scaled GameBoy screen to allow for centering
+    // Add 60 pixels of padding on each side (30 pixels on each edge)
+    let window_width = (SCREEN_WIDTH * 3 + 60) as u32;
+    let window_height = (SCREEN_HEIGHT * 3 + 60) as u32;
+    let window = video_subsystem.window("GameBoy Emulator", window_width, window_height)
+        .position_centered()
+        .build()
+        .unwrap();
+
+    // Create a renderer
+    let mut canvas = window.into_canvas().build().unwrap();
+    let texture_creator = canvas.texture_creator();
+    let mut texture = texture_creator.create_texture_streaming(
+        sdl2::pixels::PixelFormatEnum::RGB24,
+        SCREEN_WIDTH as u32,
+        SCREEN_HEIGHT as u32
+    ).unwrap();
+
+    // Define the GameBoy color palette (from lightest to darkest)
+    let gb_colors = [
+        Color::RGB(155, 188, 15),  // Light green
+        Color::RGB(139, 172, 15),  // Medium green
+        Color::RGB(48, 98, 48),    // Dark green
+        Color::RGB(15, 56, 15),    // Darkest green
+    ];
+
+    // Initialize the GameBoy
+    let boot_rom = std::fs::read("boot/dmg.bin").unwrap();
+    let game_rom = GameRom::load("dmg-acid2.gb");
 
     let mut gameboy = CPU{
-        registers:Registers{a:0,b:0,c:0,d:0,e:0,f:FlagsRegister::from(0),h:0,l:0},
+        registers: Registers{a:0,b:0,c:0,d:0,e:0,f:FlagsRegister::from(0),h:0,l:0},
-        pc:0,
+        pc: 0,
-        bus:MemoryBus{
+        bus: MemoryBus{
             memory: [0xFFu8; 0xFFFF+1],
-            gpu:GPU{ vram: vec![0xFFu8;VRAM_END-VRAM_BEGIN+1], tile_set: [[[TilePixelValue::Zero; 8]; 8]; 384] },
+            gpu: GPU::new(vec![0xFFu8;VRAM_END-VRAM_BEGIN+1]),
             rom: game_rom,
             boot: boot_rom,
             flat_ram: false
@@ -1080,12 +1211,113 @@ fn run_gameboy() {
         interrupts_enabled: false,
     };
     gameboy.init();
-    let mut count =0;
+    // Set up event handling
-    loop {
+    let mut event_pump = sdl_context.event_pump().unwrap();
-        count += 1;
+
-        if count % 1_000_000 == 0 {
+    // Main loop
-            println!("PC: {:04X}, {count}", gameboy.pc);
+    let mut count = 0;
+    let mut last_render_time = Instant::now();
+    let frame_duration = Duration::from_millis(16); // ~60 FPS
+
+    'running: loop {
+        // Handle events
+        for event in event_pump.poll_iter() {
+            match event {
+                Event::Quit {..} | 
+                Event::KeyDown { keycode: Some(Keycode::Escape), .. } => {
+                    break 'running;
+                },
+                _ => {}
             }
+        }
+
+        // Execute instructions until it's time to render again
+        let now = Instant::now();
+
+        // Execute a minimum number of instructions per frame to ensure progress
+        let min_instructions_per_frame = 10000;
+        let mut instructions_this_frame = 0;
+
+        while now.duration_since(last_render_time) < frame_duration || instructions_this_frame < min_instructions_per_frame {
             gameboy.execute_next_instruction();
+            count += 1;
+            instructions_this_frame += 1;
+
+            // Avoid getting stuck in this loop if it takes too long
+            if instructions_this_frame > min_instructions_per_frame * 2 {
+                println!("Warning: Executed {} instructions this frame, breaking loop", instructions_this_frame);
+                break;
+            }
+        }
+
+        // Log the number of instructions executed this frame
+        if count % 60 == 0 {  // Log once per second
+            println!("Executed {} instructions this frame", instructions_this_frame);
+        }
+
+        // Render the screen
+
+        // Debug: Check if the screen buffer has any non-zero values
+        let mut non_zero_pixels = 0;
+        for y in 0..SCREEN_HEIGHT {
+            for x in 0..SCREEN_WIDTH {
+                if gameboy.bus.gpu.screen_buffer[y][x] > 0 {
+                    non_zero_pixels += 1;
+                }
+            }
+        }
+
+        // Track changes in the screen buffer
+        static mut LAST_BUFFER_HASH: u64 = 0;
+        static mut FRAMES_SINCE_CHANGE: u32 = 0;
+        static mut LAST_CHANGE_COUNT: u32 = 0;
+
+        // Calculate a simple hash of the screen buffer
+        let mut buffer_hash: u64 = 0;
+        for y in 0..SCREEN_HEIGHT {
+            for x in 0..SCREEN_WIDTH {
+                buffer_hash = buffer_hash.wrapping_mul(31).wrapping_add(gameboy.bus.gpu.screen_buffer[y][x] as u64);
+            }
+        }
+
+
+        texture.with_lock(None, |buffer: &mut [u8], pitch: usize| {
+            for y in 0..SCREEN_HEIGHT {
+                for x in 0..SCREEN_WIDTH {
+                    let color_idx = gameboy.bus.gpu.screen_buffer[y][x] as usize;
+                    let color = gb_colors[color_idx];
+
+                    let offset = y * pitch + x * 3;
+                    buffer[offset] = color.r;
+                    buffer[offset + 1] = color.g;
+                    buffer[offset + 2] = color.b;
+
+                    // Debug: Print color values for a few pixels
+                    if count % 60 == 0 && y == 75 && x < 5 {
+                        println!("Pixel at ({}, {}): color_idx={}, RGB=({}, {}, {})",
+                                 x, y, color_idx, color.r, color.g, color.b);
+                    }
+                }
+            }
+        }).unwrap();
+
+        // Clear the canvas with a dark color for the border
+        canvas.set_draw_color(Color::RGB(24, 24, 24)); // Dark gray
+        canvas.clear();
+
+        // Calculate the position to center the texture in the window
+        let window_width = (SCREEN_WIDTH * 3 + 60) as u32;
+        let window_height = (SCREEN_HEIGHT * 3 + 60) as u32;
+        let x = (window_width - (SCREEN_WIDTH * 3) as u32) / 2;
+        let y = (window_height - (SCREEN_HEIGHT * 3) as u32) / 2;
+
+        canvas.copy(&texture, None, Some(Rect::new(x as i32, y as i32, 
+                                                 (SCREEN_WIDTH * 3) as u32, 
+                                                 (SCREEN_HEIGHT * 3) as u32))).unwrap();
+        canvas.present();
+
+        // Update timing
+        last_render_time = now;
+
     }
 }