Numberblocks 11-20 Activity Book & Interactive PenThis interactive and multisensory way of learning encourages children to learn independently through positive reinforcement and gentle redirection. Review the question on a page and make your selection by touching the tip of the interactive Numberblocks Hot Dots pen to the center of a dot. Choose the correct answer and see the pen glow green. Select the incorrect answer and the pen glows red. Activate the audio button to hear fun Numberblocks sounds.