Physics-Engine/PhysicsEngine/Physics/Bodies/Circle.cs

using System;
using System.Numerics;
using Raylib_cs;

namespace PhysicsEngine
{
    public class Circle : Body
    {
        public float Radius;

        public Circle(Vector2 position, float radius, float mass)
        {
            Position = position;
            Radius = radius;
            Mass = mass;
            
            if (mass > 0.0f)
            {
                MomentOfInertia = 0.5f * mass * radius * radius;
            }
        }

        public override void Draw(float pixelsPerMeter = 100.0f)
        {
            DrawHelper.DrawCircleBody(Position, Radius, Rotation, BaseColor, pixelsPerMeter);
        }

        public override void ApplyAerodynamicDrag(float dt)
        {
            if (DragCoefficient <= 0.0f) return;

            const float airDensity = 1.225f;
            float area = Radius * 2.0f;
            float speed = Velocity.Length();

            if (speed > 0.0001f)
            {
                Vector2 dragDir = -Vector2.Normalize(Velocity);
                float dragMagnitude = 0.5f * airDensity * speed * speed * DragCoefficient * area;
                ApplyForce(dragDir * dragMagnitude);
            }
        }
    }
}