画面を揺らす

# include <Siv3D.hpp>

class ScreenShake : public IEffect
{
private:

    double m_maxOffset, m_lengthMillisec;

public:

    ScreenShake(double maxOffset, double lengthMillisec)
        : m_maxOffset(maxOffset)
        , m_lengthMillisec(lengthMillisec) {}

    bool update(double timeSec) override
    {
        const double timeMillisec = timeSec * 1000.0;

        const Vec2 offset = RandomVec2(Circle(m_maxOffset * Max(1.0 - timeMillisec / m_lengthMillisec, 0.0)));

        Graphics2D::SetTransform(Mat3x2::Translate(offset));

        return timeMillisec < m_lengthMillisec;
    }
};

void Main()
{
    const Texture texture0(L"Example/Windmill.png");
    const Texture texture1(L"Example/Siv3d-kun.png");
    const Font font(15);
    Effect effect;

    while (System::Update())
    {
        if (effect.num_effects == 0 && Input::MouseL.clicked)
        {
            effect.add<ScreenShake>(16, 600);
        }

        effect.update();

        texture0.draw();
        texture1.draw(300, 0);

        Graphics2D::SetTransform(Mat3x2::Identity());

        RoundRect(40, 380, 560, 80, 3).draw(Color(20, 80, 200, 230));

        if (effect.num_effects != 0)
        {
            font(L"攻撃!").draw(60, 390);
        }
    }
}