The second half of Puzzle mode involves clearing the same figure twice. The figure is considered "cleared" as soon as the timeline passes over the end of it. However, only blocks the timeline passes AFTER you've completed the figure will actually be deleted. If you wait until the timeline has passed over most of the figure before actually placing the final block, you will accomplish the first clear--but only the rightmost edge of the figure will be deleted. For most x2 Puzzles, this makes it ridiculously simple to complete the figure a second time and clear the stage.