This minimalistic device emulates a cozily flickering fireplace by applying a random walk PWM on two output pins of an ATtiny13. Simply connect a red LED to pin 5 and a yellow LED to pin 6 (using appropriate series resistors of course).
Example:
GND--[100nF]--VCC
+--------+
-|1 ° 8|--VCC
-|2 7|-
-|3 6|--[330R]--|>--GND
GND--|4 5|--[330R]--|>--GND
+--------+
Consider adding 10uF to VCC/GND when using longer power wires. Enjoy!