private boolean checkAllRows() {
		boolean changed = false;
		int numberChanged = 0;
		//goes down so that rows aren't skipped
		for(int z = height - SAFE_HEIGHT; z >= 0; z--) {
			if(checkSingleRow(z)) {
				changed = true;
				numberChanged++;
				for(int i = z + 1; i < height; i++) {
					// z + 1 so that the deleted plane is overwritten first
					lowerPlane(i);
				}
			}
		}
		score += 100 * numberChanged * numberChanged;
		return changed;
	}