A handmade game engine built from scratch following platform abstraction principles. This is a learning project focused on understanding low-level game engine architecture without relying on large frameworks.

Goliath is a minimal game engine implementation that demonstrates:

• Platform abstraction layer design
• Cross-platform input handling (keyboard + game controllers)
• Audio output using ring buffers
• Software rendering to offscreen buffers
• Memory management and allocation strategies

The project currently implements two platform layers:

• macOS native (Objective-C++ with Cocoa/AppKit)
• SDL2 (cross-platform)

Both share the same platform-independent game code.

• Platform-Independent Game Layer: Core game logic separated from platform code
• Input System: Unified keyboard and game controller input abstraction
  • Keyboard mapped to controller (Controllers[0])
  • Physical controllers mapped to Controllers[1-5]
  • Double-buffering pattern for input state
• Audio System: Ring buffer-based audio output with sine wave generation
• Graphics: Simple software rendering (animated gradient demo)
• Memory: Custom memory allocation with permanent and transient storage
• Debug File I/O: Platform-independent file read/write utilities

goliath/
├── src/
│   ├── goliath.cpp         # Platform-independent game logic
│   ├── goliath.h           # Game API and data structures
│   ├── sdl_goliath.cpp     # SDL2 platform layer
│   ├── sdl_goliath.h       # SDL platform definitions
│   └── macos/
│       ├── osx_main.mm     # macOS native platform layer
│       └── osx_main.h      # macOS platform definitions
├── build.sh                # SDL build script
└── run.sh                  # Run SDL build

For SDL2 build:

• SDL2 library (brew install sdl2 on macOS)
• C++ compiler (clang/gcc)

For macOS native build:

• macOS with Xcode Command Line Tools
• Objective-C++ compiler

SDL2 version (recommended for cross-platform):

./build.sh          # Builds to build/goliath
./run.sh            # Builds and runs

macOS native version:

cd src/macos
./build_osx.sh      # Builds macOS.app bundle
./run_osx.sh        # Builds and runs

• WASD: Movement (mapped to controller D-pad)
• Arrow Keys: Action buttons
• Q/E: Shoulder buttons
• Space: Start button
• ESC: Back button
• Alt+F4: Quit (SDL)

Game controllers are automatically detected and supported.

The engine uses a clean platform abstraction architecture:

1. Platform Layer (SDL/macOS): Handles windowing, input events, audio callbacks
2. Platform-Independent Layer (goliath.cpp): Game logic, rendering, sound generation
3. Data Flow: Platform → Game → Platform (via function pointers and structs)

Key patterns:

• Double-buffering for input state
• Ring buffer for audio streaming
• Callback-based debug I/O
• Union types for flexible data access

This is an educational project focused on learning engine architecture. Current capabilities:

• Displays animated gradient (controlled by keyboard/gamepad)
• Plays sine wave audio tone
• Demonstrates platform abstraction patterns
• Shows input handling architecture

Future plans may include: sprite rendering, tile maps, entity systems, and game-specific logic.

This project is licensed under the MIT License - see the LICENSE.md file for details.