Press the top number buttons to make the Target number. The variable in the middle shows you the current total. Selected numbers will be outlined in red. To remove a number just click it again and the out line will go away. Give your best time after completing Level 13.
Also see the Magical Mind Reader: https://scratch.mit.edu/projects/1709159/ It is using the same technique. All computers also save everything this way, it is called the "Binary System".
