void specialKeys(int key, int x, int y)//key由系统自动识别获取
{
    /*
     判断：x值以正方形最左边为基准；y值以正方形最上边为基准；
     blockX、blockY值不能赋值于常量——因为vVerts四个点是动态变化的（SpecialKeys也会随之被动态调用）；
     */
    GLfloat blockX = vVerts[0];
    GLfloat blockY = vVerts[10];
    GLfloat stepSize = 0.025;
    
    if (key == GLUT_KEY_UP) {
        blockY += stepSize;
    }
    
    if (key == GLUT_KEY_DOWN) {
        blockY -= stepSize;
    }
    
    if (key == GLUT_KEY_LEFT) {
        blockX -= stepSize;
    }
    
    if (key == GLUT_KEY_RIGHT) {
        blockX += stepSize;
    }
    
    //触碰到窗口边界处理
    if (blockX < -1.0) {
        blockX = -1.0;
    }
    
    if (blockX > (1.0-blockSize*2)) {
        blockX = 1.0-blockSize*2;
    }
    
    if (blockY > 1.0) {
        blockY = 1.0;
    }
    
    if (blockY < -1.0+blockSize*2) {
        blockY = -1.0+blockSize*2;
    }
    
    //正方形四个顶点坐标动态赋值
    vVerts[0] = blockX;
    vVerts[1] = blockY-blockSize*2;
    
    vVerts[3] = blockX+blockSize*2;
    vVerts[4] = blockY-blockSize*2;
    
    vVerts[6] = blockX+blockSize*2;
    vVerts[7] = blockY;
    
    vVerts[9] = blockX;
    vVerts[10] = blockY;
    
    triangleBatch.CopyVertexData3f(vVerts);
    
    glutPostRedisplay();
}