There are 12 dots arranged in a 3 by 4 square similarly to "nine dots." Connect all of them with 5 straight lines without lifting your pencil, ending at the same point you started at. You cannot cross the same point twice, but the lines themselves may cross. There are no tricks here!
Bonus: Try doing the same with a 4 by 4 square with 16 dots and 6 lines (it's similar).