Original game idea by @Igor.
Original circuit: http://everycircuit.com/circuit/5811537524555776
When counter stops it's GAME OVER. If you reach 99 you complete the game :D
Bird is the orange voltage. Push the button to pump current into the capacitor and fly up. Release button to discharge capacitor via resistor to descend.
Two comparators detect the crash. OR gate turns the series pass transistor on which stops the counter.