I'm new in Raspberry Pi world, so please excuse my possible mistakes.
This project is made for my kids. Retro games are usually less violent, more entertaining, and despite lesser graphics quality, often more attractive to kids. I found nice ROM, RetroPie, distribution for Raspberry Pi based on armbian with Emulation station as shell.
It wouldn't be nice to attach it to my (only) big screen TV, as kids tend to occupy it at random intervals, and, as expected, mostly in times I want to watch TV. So I've attached RPi to 15 inch LCD monitor. For that I had to use HDMI to VGA converter ($6 on ebay). Also, to RPi I've attached two gamepads.
As I wanted this gaming station to be as portable as it gets, but on normal desktop computing scale (not some handheld console), I have decided to fully integrate RPi to LCD. I didn't want to cut whole screen, but rather "attach" everything to it.
In my plans I've realized that it will have whole bunch of cables behind, and it would need two separate power cables (one for monitor, and one for RPi). To make it more portable, I have embedded power supply for RPi in the bottom of monitor stand. LCD and this RPi power supply are connected with one power cable... :-)
Step 1: Raspberry Pi Power Supply Problem
Raspberry Pi has real OS, Armbian. It is possible to shut it down almost as normal desktop computer. Almost - after powering it down, you have to unplug USB cable and insert it back to power RPi back up.
That is one thing I anted to change. So I've made my Arduino Nano as sensor for RPi. Nano is connected to RPi's GND and pin 14 (UART_TX pin). When RPi is powered up, this pin has 3.3 volts, and it cuts power to it when RPi is powered off. Nano pin D5 is input that "senses" that change and triggers relay (pin D6) to cut power completely. I've also added one button to Nano pin D7, which is in HIGH position, and when that button is pressed, it makes pin LOW. That triggers relay, which enables power to RPi, from which pin 14 is then HIGH (or with 3.3V current). This is, as far as I know, only power supply for RPi that works in that way. My Arduino sketch is attached here :-)
In that sketch I have enabled some serial printouts, which can be commented out, and are for setup only...
Step 2: Encased
Everything is encased (old tupperware-like container, cut to fit on top of RPi - to make it kid-tamper-proof). I have used a lot of hot glue to fix everything in place.
I have ordered short VGA cable, so this horrid 1,5 meter long one will be replaced. One USB port is "extended" outside, to provide easy access to it for gamepads (two gamepads on one USB cable - when I get some cash, I'll buy two wireless gamepads, but this USB is convenient to have it outside).
Button for re-powering RPi is glued at the back, but when I paint case/cover, it will be mounted somewhere in front.