Update README with raylib submodule instructions

Improvements:
- Add "Getting Started" section with git clone instructions
- Document how to initialize raylib submodule
- Remove libraylib-dev from dependencies (using submodule instead)
- Remove manual raylib build instructions
- Clarify build process (raylib built automatically)
- Add make rebuild and make clean-all commands

This makes it clearer for users cloning the project that raylib
is included as a submodule and will be built automatically.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

README.md

@@ -12,9 +12,26 @@ A 3D orbital mechanics simulation using a 2-body gravitational model with sphere
 - **Simulation controls** (pause, resume, speed adjustment)
 - Solar system and binary star example configurations
 
-## Dependencies (Debian 13)
+## Getting Started
 
-Install the required packages:
+### Cloning the Project
+
+This project includes raylib as a git submodule. Clone with submodules:
+
+```bash
+git clone --recursive https://github.com/yourusername/claudes_game.git
+cd claudes_game
+```
+
+If you already cloned without `--recursive`, initialize the submodule:
+
+```bash
+git submodule update --init --recursive
+```
+
+### Dependencies (Debian 13)
+
+Install the required system packages:
 
 ```bash
 sudo apt-get update
@@ -22,7 +39,6 @@ sudo apt-get install -y \
     build-essential \
     g++ \
     make \
-    libraylib-dev \
     libx11-dev \
     libxcursor-dev \
     libxrandr-dev \
@@ -32,30 +48,28 @@ sudo apt-get install -y \
     libglu1-mesa-dev
 ```
 
-If `libraylib-dev` is not available in the repositories, you can build raylib from source:
+**Note**: You don't need to install raylib separately - it's included as a git submodule and will be built automatically by the Makefile.
+
+### Building
 
 ```bash
-# Install raylib build dependencies
-sudo apt-get install -y cmake git
-
-# Clone and build raylib
-git clone https://github.com/raysan5/raylib.git
-cd raylib
-mkdir build && cd build
-cmake .. -DBUILD_SHARED_LIBS=ON
 make
-sudo make install
-sudo ldconfig
-cd ../..
 ```
 
-## Building
+This will:
+1. Build raylib from the submodule (first time only)
+2. Compile all source files
+3. Create the `orbit_sim` executable in the project directory
 
+To clean and rebuild:
 ```bash
-make
+make rebuild
 ```
 
-This will create the `orbit_sim` executable in the project directory.
+To clean everything including raylib:
+```bash
+make clean-all
+```
 
 ## Running