CODE:

#include 
#include 
#include 
#include 
#include 
using namespace Linear;
 
static const double dt = 1.0 / 60;

class Entity
{
public:
	virtual void Update() = 0;
	virtual void Draw() const = 0;
};


class Particle
	: public Entity
{
public :
    //質点の作成
    static std::shared_ptr Create( double m, Vector s, Vector v )
    {
        return std::shared_ptr( new Particle(m,s,v) );
    }
 
    //質点に力を加える
    void AddForce( Vector f )
    {
        f_ += f;
    }
 
    //質点の位置を取得
    const Vector S() const
    {
        return s_;
    }
 
    //質点の速度を取得
    const Vector V() const
    {
        return v_;
    }
 
    //質点の更新
    virtual void Update()
    {
        //運動方程式に従い加速度、速度、位置を更新
        a_ = f_ / m_;
        v_ += a_ * dt;
        s_ += v_ * dt;
 
        //力を0に
        f_ = Vector();
    }
 
    virtual void Draw() const
    {
        DxLib::DrawCircle( s_.x, s_.y, 10, DxLib::GetColor( 0x2C, 0xCC, 0x7c ) );
    }
 
private :
    double          m_; //質量        
    Vector  s_; //位置
    Vector  v_; //速度
    Vector  a_; //加速度
    Vector  f_; //力
 
private:
    Particle( double m, Vector s, Vector v )
        :m_(m),s_(s),v_(v)
    {
    }
    Particle( const Particle& );
    Particle& operator=( const Particle& );
};
 
class Spring
	: public Entity
{
public:
	 //質点の作成
    static std::shared_ptr Create( std::weak_ptr p1, std::weak_ptr p2, double k, double l )
    {
        return std::shared_ptr( new Spring(  p1,  p2, k, l ) );
    }


	void Update()
	{
		auto p1 = p1_.lock();
		auto p2 = p2_.lock();
		if( p1 && p2 )
		{
			//質点間の相対位置ベクトルを取得
			Vector d = p2->S() - p1->S();
			//質点間の距離を算出
			double dist = sqrt(double(d*d));

			//相対位置ベクトルの単位ベクトルを計算
			Vector de = d / dist;

			//与える力は大きさk*(dist-l)、向きde
			Vector f = de * k_*(dist-l_);
			p1->AddForce( f );
			p2->AddForce( -f );
		}
	}

	//ばねの描写
	void Draw() const
	{
		auto p1 = p1_.lock();
		auto p2 = p2_.lock();
		if( p1 && p2 )
		{
			const int rep = 11;
			Vector d = p2->S() - p1->S();
			Vector de = d / rep;
			
			d.Normalize();
			Vectordn = GetNormalVector2D( d );
			dn *= l_ / 10.0;
				
			double xtemp = p1->S().x; double ytemp = p1->S().y;
			double orientation = 1;
			for( int i = 1; i  temp =  p1->S()+de*i + dn*orientation;
				DxLib::DrawLine( xtemp,ytemp, temp.x, temp.y, 0xFF0000, 1 );
				orientation *= -1;
				xtemp = temp.x, ytemp = temp.y;
			}
			DxLib::DrawLine( xtemp,ytemp, p2->S().x, p2->S().y, 0xFF0000, 1 );
		}
	}

private:

	//質点1, 質点2, ばね定数k, ばねの自然長l
	Spring( std::weak_ptr p1, std::weak_ptr p2, double k, double l )
		:p1_(p1),p2_(p2),k_(k),l_(l)
	{
	}

	std::weak_ptr p1_;
	std::weak_ptr p2_;
	double k_;
	double l_;
};

//質点に毎フレームごとに力を与えるクラス
class Environment
{
public:
    static Environment& Instance()
    {
        static Environment e;
        return e;
    }
 
    //質点を設定
    void SetEntity( std::weak_ptr entity )
    {
        entities_.push_back(entity);
    }
 
 
    void Update()
    {
        for( auto it = entities_.begin(); it != entities_.end(); ++it )
		{
			if( auto p = it->lock() )
			{
				p->Update();
			}
		}
    }
 
    void Draw()
    {
        for( auto it = entities_.begin(); it != entities_.end(); ++it )
		{
			if( auto p = it->lock() )
			{
				p->Draw();
			}
		}
    }
 
private:
    std::vector> entities_;
private:
	Environment(){}
    Environment( const Environment& );
    Environment& operator=( const Environment& );
};
 
 
  
 
int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow )
{
    ChangeWindowMode(true);
    if( DxLib_Init() ( 350, 100, 0 ), Vector(200,0,0) );
    auto p2 = Particle::Create( 0.2, Vector( 250, 100, 0 ), Vector(-200,0,0) );
	auto s12  = Spring::Create( p1,p2,5,150 );

	Environment::Instance().SetEntity( p1 );
	Environment::Instance().SetEntity( p2 );
	Environment::Instance().SetEntity( s12 );
 
	//質点2つとばね（質点の初速度の関係で回転する）
	auto p3 = Particle::Create( 0.2, Vector( 350, 200, 0 ), Vector(200,70,0) );
    auto p4 = Particle::Create( 0.2, Vector( 250, 200, 0 ), Vector(-200,-70,0) );
	auto s34  = Spring::Create( p3,p4,5,100 );

	Environment::Instance().SetEntity( p3 );
	Environment::Instance().SetEntity( p4 );
	Environment::Instance().SetEntity( s34 );

	//n質点系（質点の初速度の関係で回転する）（カオス的）
	auto p5 = Particle::Create( 0.2, Vector( 150, 400, 0 ), Vector(200,70,0) );
    auto p6 = Particle::Create( 0.2, Vector( 250, 400, 0 ), Vector(100,70,0) );
	auto p7 = Particle::Create( 0.2, Vector( 350, 400, 0 ), Vector(-100,-70,0) );
	auto p8 = Particle::Create( 0.2, Vector( 450, 400, 0 ), Vector(-200,-70,0) );
	auto s56  = Spring::Create( p5,p6,5,100 );
	auto s67  = Spring::Create( p6,p7,10,100 );
	auto s78  = Spring::Create( p7,p8,5,100 );

	Environment::Instance().SetEntity( p5 );
	Environment::Instance().SetEntity( p6 );
	Environment::Instance().SetEntity( p7 );
	Environment::Instance().SetEntity( p8 );
	Environment::Instance().SetEntity( s56 );
	Environment::Instance().SetEntity( s67 );
	Environment::Instance().SetEntity( s78 );

    while( ProcessMessage() == 0 && CheckHitKey( KEY_INPUT_ESCAPE ) == 0 )
    {
        ClearDrawScreen() ;
        //メインループ
        {
            Environment::Instance().Update();
            Environment::Instance().Draw();
        }
        ScreenFlip() ;
    }
 
    DxLib_End() ;
    return 0 ;
}