I have attempted to create a round QPushButton using Styles, however it is still coming out rectangular. Could someone point out where I am going wrong please?

Qt Code: 
  1. #ifndef MAINWINDOW_H
  2. #define MAINWINDOW_H
  3.  
  4. #include <QMainWindow>
  5.  
  6. class RoundPushbutton;
  7.  
  8. class MainWindow : public QMainWindow
  9. {
  10.     Q_OBJECT
  11.  
  12. public:
  13.     explicit MainWindow(QWidget *parent = 0);
  14.  
  15. private:
  16.     RoundPushbutton *roundButton;
  17. };
  18.  
  19. #endif // MAINWINDOW_H
To copy to clipboard, switch view to plain text mode 

Qt Code: 
  1. #include "mainwindow.h"
  2. #include "roundpushbutton.h"
  3.  
  4. #include <QVBoxLayout>
  5. #include <QPushButton>
  6.  
  7. MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
  8. {
  9.     QWidget *window = new QWidget(this);
  10.     QVBoxLayout *vlay = new QVBoxLayout(window);
  11.     QPushButton *btn1 = new QPushButton("1");
  12.     vlay->addWidget(btn1);
  13.     QPushButton *btn2 = new QPushButton("2");
  14.     vlay->addWidget(btn2);
  15.     RoundPushbutton *roundButton = new RoundPushbutton();
  16.     vlay->addWidget(roundButton);
  17.     window->setLayout(vlay);
  18.     setCentralWidget(window);
  19. }
To copy to clipboard, switch view to plain text mode 

Qt Code: 
  1. #ifndef ROUNDPUSHBUTTON_H
  2. #define ROUNDPUSHBUTTON_H
  3.  
  4. #include <QPushButton>
  5.  
  6. class RoundPushbutton : public QPushButton
  7. {
  8. public:
  9.     explicit RoundPushbutton(QWidget *parent = 0);
  10. };
  11.  
  12. #endif // ROUNDPUSHBUTTON_H
To copy to clipboard, switch view to plain text mode 

Qt Code: 
  1. #include "roundpushbutton.h"
  2.  
  3. #include <QPushButton>
  4.  
  5. RoundPushbutton::RoundPushbutton(QWidget *parent)
  6.     : QPushButton(parent)
  7. {
  8.     QPushButton *button = new QPushButton();
  9.     //button->setGeometry(QRect(100, 100, 300, 300));
  10.     button->setText("Quit");
  11.     button->setFlat(true);
  12.     button->setAttribute(Qt::WA_TranslucentBackground);
  13.     button->setStyleSheet(
  14.         "background-color: red;"
  15.         "border: 1px solid black;"  //outline
  16.         "border-radius: 150px;"     //corners
  17.         "color: lightGray; "        //text
  18.         "font-size: 35px;"
  19.         );
  20. }
To copy to clipboard, switch view to plain text mode 

Instead of 2 normal QPushbuttons followed by a round one, they all look normal.
Thank you.