Resolved that annoying gravity bug and added trajectories, a grid, keyboard navigation and logarithimic scale

README.md

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+# 3D Gravity Simulator Documentation
+
+## Overview
+
+This 3D Gravity Simulator is a C++ program that visualizes the gravitational interactions between celestial bodies in a simplified solar system model. It uses OpenGL for rendering and GLFW for window management and user input.
+
+## Program Structure
+
+The simulator consists of several key components:
+
+1. `Simulator`: Handles the physics calculations and updates the positions of celestial bodies.
+2. `Renderer`: Manages the 3D rendering of the celestial bodies, trajectories, and grid.
+3. `CelestialBody`: Represents individual celestial bodies with properties like mass, position, and velocity.
+
+## Physics Implementation
+
+### Gravitational Force
+
+The simulator uses Newton's law of universal gravitation to calculate the forces between celestial bodies. The gravitational force between two bodies is given by:
+
+$$ F = G \frac{m_1 m_2}{r^2} $$
+
+Where:
+- $F$ is the gravitational force between the two bodies
+- $G$ is the gravitational constant ($$6.67430 \times 10^{-11} \, \text{N} \cdot \text{m}^2 / \text{kg}^2$$)
+- $m_1$ and $m_2$ are the masses of the two bodies
+- $r$ is the distance between the centers of the two bodies
+
+### Motion Update
+
+The motion of each celestial body is updated using numerical integration. We use a simple Euler method for updating positions and velocities:
+
+1. Calculate the net force on each body
+2. Calculate acceleration: $$ \vec{a} = \frac{\vec{F}}{m} $$
+3. Update velocity: $$ \vec{v}_{new} = \vec{v}_{old} + \vec{a} \Delta t $$
+4. Update position: $$ \vec{x}_{new} = \vec{x}_{old} + \vec{v}_{new} \Delta t $$
+
+Where $\Delta t$ is the time step of the simulation.
+
+## Rendering
+
+The program uses OpenGL to render the 3D scene:
+
+- Celestial bodies are represented as spheres with sizes proportional to their masses (using a logarithmic scale).
+- A grid is drawn to provide a reference plane.
+- Trajectories of the bodies are drawn as lines, fading out over time.
+- The camera can be controlled using WASD keys for movement and the mouse for orientation.
+
+## Limitations and Simplifications
+
+1. The simulation uses a fixed time step, which can lead to inaccuracies in long-term simulations.
+2. The Euler method for numerical integration is simple but can accumulate errors over time.
+3. The scale of the celestial bodies and their distances are not to true scale to make visualization easier.
+4. Relativistic effects are not considered; the simulation uses classical Newtonian mechanics.
+