Behold - the WatchBoy DX! 
That’s right, I designed a replacement PCB for the GameBoy to turn it into a seven-segment LCD clock!
(inspired by the 90’s “WatchBoy” wristwatch that took the shape of an itty bitty GameBoy)
This is using an ATmega169PA for its built-in LCD Controller, and a 32.768kHz crystal for time-keeping.
It plays a familiar tune while setting the time using Up / Down, and also has a built-in “mini game” when B is pressed… 
I have a few PCBs to spare from the ‘prototype’ run, and am waiting on another batch of newer boards coming from China.
Here is the code:
I also found a bunch of neat ideas for seven-segment games while researching the project:
Arduino Reaction Timer Game - YouTube
7 Segment Racing Game Demo - YouTube
4 digit 7 segment number guessing game - YouTube
Pong Game on Seven Segment Display Altera Board Cyclone II Verilog - YouTube