Nickjohnson posted his minimatrix project in the forum. It’s AVR powered 8×8 LED matrix, with an IR sensor for communication.
It has just 8 parts in its BoM: A one-color 3cm LED matrix, an ATTiny2313/4313 to power and drive it, an 8-way resistor network, a battery holder, and two decoupling capacitors. Finally, it has a footprint for a thru-hole IR LED, making it possible to add interactivity easily and with little overhead. The IR LED footprint is situated on the back, so it can be placed then bent upwards to protrude above the matrix.
Via the forum.