Game Boy Emulator

A Nintendo Game Boy emulator written in C++ using SDL3, developed to gain a deeper understanding of computer architecture, hardware emulation, graphics rendering, memory management, and low-level systems programming.

The emulator recreates the core hardware of the original Nintendo Game Boy, including the CPU, memory subsystem, graphics processor (PPU), timers, interrupts, audio, input handling, and multiple Memory Bank Controllers (MBCs).

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Features

CPU

• Complete Game Boy CPU instruction set
• CB-prefixed instructions
• Register and flag emulation
• Stack operations
• Control flow instructions

Memory

• Full 64 KB memory map
• Memory-mapped I/O
• DMA transfers
• Hardware register initialization

Graphics (PPU)

• Background rendering
• Window rendering
• Sprite rendering
• Timer emulation
• Interrupt handling
• DMA transfers
• Joypad input handling
• ROM-only cartridge support
• Compatibility with commercial ROM-only games
• Successfully passes all Blargg CPU test ROMs
• Audio Processing Unit (APU)
• Scanline-based rendering
• LCD timing
• VBlank and LCD interrupts
• Scanline-based rendering
• LCD timing
• VBlank and LCD interrupts

Timers & Interrupts

• DIV and TIMA timers
• Interrupt handling
• Cycle-based synchronization

Input

• Joypad emulation
• Keyboard controls

Audio

• Audio Processing Unit (APU)
• Real-time sound output

Cartridge Support

• ROM Only
• MBC1
• MBC2
• MBC3
• MBC5

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Controls

Keyboard	Game Boy Button
W	Up
A	Left
S	Down
D	Right
J	A
K	B
Enter	Start
Right Shift	Select

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Project Structure

GameBoyEmulator/
│
├── src/
├── include/
├── docs/
│   ├── DEVELOPMENT_LOG.md
│   └── lessons/
├── ROM/
├── assets/
├── CMakeLists.txt
└── README.md

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Building the Project

Requirements

• C++17 compatible compiler
• CMake (3.15 or later)
• SDL3

Clone the Repository

git clone https://github.com/CassideousxD/GameBruh.git
cd GameBruh

Build

mkdir build
cd build

cmake ..
cmake --build .

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Running the Emulator

From the build directory:

./GameBruh

or

./bin/GameBruh

(depending on your build configuration)

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Loading ROMs

Place Game Boy ROM files (.gb) inside the ROM/ directory.

Example:

ROM/
├── Tetris.gb
├── DrMario.gb
├── PokemonRed.gb
└── Zelda.gb

Launch the emulator and load the desired ROM.

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Documentation

Detailed documentation is available in the docs directory.

File	Description
DEVELOPMENT_LOG.md	Development milestones and progress
lessons/	Detailed explanations of Game Boy hardware concepts

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Learning Objectives

This project was developed to better understand:

• Computer Architecture
• Hardware Emulation
• CPU Design
• Memory Management
• Interrupt Handling
• Graphics Rendering
• Digital Audio
• Object-Oriented Design
• Low-Level Systems Programming

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Future Improvements

• Save states
• Pause and resume
• ROM selection menu
• Screenshot support
• Controller support
• Display customization
• Performance optimizations
• Expanded ROM compatibility

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References

• Pan Docs
• Game Boy CPU Manual
• Blargg Test ROMs
• Mooneye Test Suite

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License

This project is licensed under the MIT License.