My wife was playing with Emmett's cube gears and suggested that it'd be cool with a light in it. If I'm going to all that trouble, I'm going to put in more than one light :)

https://www.youtube.com/watch?v=3Jl0vh4w2LU

I grabbed a few WS2811 pixels out of the project box and made a few changes to the cube, including scaling it up to 5 inches.

This is an early beta version of this cube. Instructions, wiring diagrams, etc will follow, and I'll probably make more changes to the pins.

This version has 9 RGB leds, 1 in the center, and 1 in each corner. I'm running it on an arduino nano using FastLED. It's powered by an 18650 3.7V battery in a case I printed (http://www.thingiverse.com/thing:535688/) that runs into the arduino and LEDs via a boost converter I salvaged from an old USB battery pack. [edit, I've been through a few batteries in this thing, and the little envelope style lipos fit better than the 18650. Right now I'm using this 2500mAh one: https://smile.amazon.com/gp/product/B01KJ07A2Q/ref=oh_aui_search_detailpage?ie=UTF8&psc=1]

I've included several versions of the pin, since some are easier to get in than others. I'm really liking pin 4, it holds it tight without being too difficult to get in. It's tricky, because orientation matters on the LED insertion due to internal structure on the waterproofed WS2811 pixels I'm using.

My current test code is up at https://github.com/bobiam/blinkygearedcube/blob/master/blinkycube.ino

You'll need to adjust some of the arrays to match your LED layout.

EDIT: The code has been updated to reflect the hall effect sensor I added to the cube on digital pin 3. Holding a magnet near the cube now advances it to the next pattern. Hoping to get a full writeup in before Maker Faire Austin 2016, but time is getting short and I've got other projects to work on too. If you don't have/want to include a hall effect sensor, you should probably use the version from this commit, which predates the sensor:
https://github.com/bobiam/blinkygearedcube/commit/c3d7d7d8d34ff5b0e07a963634f6b75ecf3ae9ce