Hemispherical Tracking Markers with Magnet recesses for playing with Pixy http://cmucam.org/projects/cmucam5/wikiPrint in bright colors for best results
I love to make things and teach people to make. You can often find me at libraries leading workshops and making a mess!I'm also a team member of wyolum.com and make Open Source Hardware, such as the Raspberry Pi Alamode