Simon game is simple you have to repeat sequence of events where number of steps increases during time. This tests your concentration and memory. You can find many versions of it in a toy shop. But being an electronics hobbyist you can build one in no time. Simoninns from instructable have built his own version of this game. His aim was to make it really tiny but not too much so it was possible at least to play with.
with only SMD parts he managed to make it a bit bigger then 1 EUR coin. There is nothing fancy in hardware – a PIC12F683 in SOIC-8 package, four SMD push buttons, four LEDs and programmer header and buzzer. Game is powered with single CR2032 V Lithium battery. One of interesting aspects in this project that it uses a single ADC pin to read four buttons. For this a three resistor voltage divider is used to generate distinguishable voltage drop. LEDs are also connected by using Charlieplexing – 3 wires to control 4 LEDs. There is still plenty time to build one to make a great gift for Christmas.