The picture shows the user interface with 7-segment display, toggle switch, 4 buttons and LEDs.
At the bottom half you see an Atmega 328p with pinouts.
Pins 0 to 7 are connected to the 7-segment display with current limiting resistors of 320 Ohm.
Pin 8 is used as input to switch between Easy and Hard. Pins 9 to 12 are inputs for the buttons.
Pin 13 is output for the red LED.
A voltage regulator 7805 is used to reduce the 9 volts of the battery to 5 volts.
The way this game works is shown in a YouTube video Game shift register
The game is to convert decimal, hex or binary numbers to another number system. With the push buttons you can move
the cursor, increase or decrease the digits, Show if the conversion has been done correctly and Restart the game.
>>> Arduino code <<<