ピアノ

# include <Siv3D.hpp>

double Synth(double t, double f)
{
    const double a = Sin(t * 523 * f * TwoPi);
    const double b = Sin(t * 523 * f * TwoPi * 2.0)*0.3;
    const double c = Sin(t * 523 * f * TwoPi * 3.0)*0.8;
    const double d = (Fraction(t * 523 * f)*2.0 - 1.0)*0.2;
    return (a + b + c + d) / 4.0*(1.0 - t);
}

void Main()
{
    const int32 numOfKeys = 22;
    std::array<Sound, numOfKeys> sounds;

    for (auto i : step(numOfKeys))
    {
        auto function = std::bind(Synth, std::placeholders::_1, Exp2((i - 5) / 12.0));
        sounds[i] = Sound(Wave(1.0s, function));
    }

    const std::array<Key, numOfKeys> keys =
    {
        Input::KeyQ, Input::Key2, Input::KeyW, Input::Key3, Input::KeyE, Input::KeyR,
        Input::Key5, Input::KeyT, Input::Key6, Input::KeyY, Input::KeyU, Input::Key8,
        Input::KeyI, Input::Key9, Input::KeyO, Input::Key0, Input::KeyP, Input::KeyAt,
        Input::KeyCaret, Input::KeyLBracket, Input::KeyYen, Input::KeyEnter
    };

    const std::array<int32, numOfKeys> keyOffset =
    {
        0, 1, 2, 3, 4, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 17, 18, 20, 21, 22, 23, 24
    };

    while (System::Update())
    {
        for (auto i : step(numOfKeys))
        {
            if (keys[i].clicked)
            {
                sounds[i].playMulti(0.3);
            }
        }

        for (auto i : step(numOfKeys))
        {
            if (keyOffset[i] % 2 == 0)
            {
                Rect(keyOffset[i] / 2 * 50, 0, 48, 400).draw(keys[i].pressed ? Palette::Pink : Palette::White);
            }
        }

        for (auto i : step(numOfKeys))
        {
            if (keyOffset[i] % 2 == 1)
            {
                Rect(35 + keyOffset[i] / 2 * 50, 0, 30, 250).draw(keys[i].pressed ? Palette::Pink : Palette::Black);
            }
        }
    }
}