Japan, Takumi Funada posted a lovely Arduino-compatible Loveduino board at Make: Tokyo Meeting 06.
I realized one sample with my PCB printer and put 18 green LEDs on digital pins (D0 to D13) and analog pins (treated here as digitals) A0 to A4.
The pin A5 has a buzzer to play melodies.I also added a power at back and a switch.
This is a very small project for fun.
You can grab the template and etch your own!
Here are the files (template) including the sketch I've made for this special issue:
1 ATMEGA 328-PU
3 100nF capacitor
1 switch button
1 power (CR2032 3V)
18 Green LEDs
1 10k resistor