Amazon offers the Ozobot Evo STEM Robot Starter Pack in Crystal White or Titanium Black for $79.99 with free shipping. That's the lowest price we could find by $18. This 1" x 1" robot reacts to lines, patterns, and color sequences on both digital and physical surfaces. It features a color optical sensor, two micro-motors, memory for up to 500 moves, visual feedback with multicolor LED lighting, interactive apps, and compatibility with iOS and Android devices.

Update: It's now available for Prime members only.