Item collision detection

Whether the player item collides with a coin is checked by the scene's checkColliding() function, which is called after the player item has moved horizontally or vertically.

Time for action - Making the coins explode

The implementation of checkColliding() looks like this:

void MyScene::checkColliding()
{
    for(QGraphicsItem* item: collidingItems(m_player)) {
        if (Coin *c = qgraphicsitem_cast<Coin*>(item)) {
            c->explode();
        }
    }
}

What just happened?

First, we call the scene's QGraphicsScene::collidingItems...