public void move() {
		//... Move the ball at the give velocity.
		m_x += m_velocityX;
		m_y += m_velocityY;        

		//... Bounce the ball off the walls if necessary.
		if (m_x < 0) {                  // If at or beyond left side
			m_x         = 0;            // Place against edge and
			m_velocityX = -m_velocityX; // reverse direction.

		} else if (m_x > m_rightBound) { // If at or beyond right side
			m_x         = m_rightBound;    // Place against right edge.
			m_velocityX = -m_velocityX;  // Reverse direction.
		}

		if (m_y < 0) {                 // if we're at top
			m_y       = 0;
			m_velocityY = -m_velocityY;

		} else if (m_y > m_bottomBound) { // if we're at bottom
			m_y       =  m_bottomBound;
			m_velocityY = -m_velocityY;
		}
	}