Pac-Man Small Arcade Game Test Mode/Lamp Test

I was trying some stuff with this thing and accidentally discovered the test mode in it.
Here are the (updated) instructions.
Take out a battery.
Hold the Volume button, the Mode button, and the Start Game button.
Put the battery back in.
You will hear beeping.
Press Mode.
Press Start Game.
You can test the backlight/lamp.
Hold Start Game to show ALL screens.
You can also test the joystick and speaker.
Up is 11111.
Down is 22222.
Left is 33333.
Right is 44444.
And if you press the volume button, it plays the Start Music in different volume levels.
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