TiniMilitia-Shooter: 2D Game Engine

Overview

A from-scratch 2D shooter game engine built to explore systems programming, real-time rendering, and game architecture. The engine runs at a locked 60 FPS with 100 simultaneously active entities, with no engine dependencies and no garbage collector.

Why Build an Engine From Scratch?

Using Unity or Unreal hides the hard problems. Building from scratch forces you to understand:

• How a game loop works (fixed timestep vs. variable)
• Why memory layout matters for cache performance
• How RAII prevents resource leaks in a system with hundreds of entities

Core Architecture

Game Loop

while (running) {
    processInput();
    update(fixedDt);   // deterministic, physics
    render();          // variable, visual interpolation
}

Using a fixed timestep for update (16.67ms) and a variable timestep for rendering makes physics deterministic and reproducible: identical input always produces identical game state.

Entity Hierarchy

Entity
  ├── Gunman  (player character)
  ├── Enemy   (AI-controlled)
  └── Bullet  (projectile)

Inheritance + polymorphism for entity update/render dispatch. Value semantics for bullets (cheap to copy, no pointer indirection) vs. reference semantics for Gunman/Enemy.

Memory Management

• RAII wrappers around all OpenGL objects (VAO, VBO, shaders): destructors release GPU resources with no manual cleanup
• Smart pointers (unique_ptr) for entity ownership: no manual new/delete
• Object pooling for bullets: avoids per-frame heap allocation at 60 FPS

Rendering Optimizations

• Sprite atlas: all textures packed into a single atlas, one texture bind per frame instead of N
• Batched rendering: all visible entities submitted in a single draw call
• Frustum culling: off-screen entities skipped entirely

Performance

Build System

CMake handles cross-platform builds (Windows/Linux/macOS):

cmake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build

External dependencies (GLFW, GLM, stb_image) managed via CMake FetchContent with no manual download required.

Tech Stack

Language: C++17 Graphics: OpenGL 3.3 · GLFW · GLAD · GLM · stb_image Build: CMake · FetchContent Patterns: RAII · Object Pooling · Batched Rendering · Fixed Timestep