public void mousePressed(MouseEvent event) {
			JButton source = (JButton) event.getSource();
			Point point = buttonMap.get(source);
			
			if(!running) {      // activate mouse listener when program isn't running
				if(SwingUtilities.isLeftMouseButton(event)) {
					lifeModel.changeCell(point.x, point.y, Color.RED);
					changeViewCell(point.x, point.y, Color.RED);
					source.setBackground(Color.RED);
				}
				else if (SwingUtilities.isRightMouseButton(event)) {
					lifeModel.changeCell(point.x, point.y, Color.GREEN);
					changeViewCell(point.x, point.y, Color.GREEN);
					source.setBackground(Color.GREEN);
				}
				else if (SwingUtilities.isMiddleMouseButton(event)){
					lifeModel.changeCell(point.x, point.y, Color.GRAY);
					changeViewCell(point.x, point.y, Color.GRAY);
					source.setBackground(Color.GRAY);
				}
				grid.validate();
			}
		}