# RetroENGINE - Run with RetroDECK
RetroENGINE is how you can run various game files directly with with RetroDECK from the desktop without starting the application.
It allows association of common system file extensions with RetroDECK.
Another option is to run the games directly RetroENGINE via CLI.
This is something that has been requested by the wider development community outside of RetroDECK.
## Will RetroENGINE detect what system I want to launch?
If you have the game file inside the corresponding `retrodeck/roms//` RetroDECK will understand what system to launch.
### What if it is not in the correct folder?
When clicked, RetroDECK will prompt a dialog window asking which system the file belongs to and then run it.
## Launch with games via CLI
You can also launch games directly with RetroENGINE via CLI.
**Example syntax:**
`flatpak run net.retrodeck.retrodeck retrodeck/roms//` (`--help` for more information).
## Examples:
In these examples, we will use the [Little Medusa - Demo](https://megacatstudios.com/pages/little-medusa) a `.nes` file called `LittleMedusa_8bitdemo.nes` from Mega Cat Studios.
### Example 1: The Game Inside the Correct Roms Folder
In this example, the `LittleMedusa_8bitdemo.nes` file is inside the `retrodeck/roms/nes` folder.
When you click on it, RetroDECK opens it with the Nintendo Entertainment System emulator, and the game starts.
RetroDECK knows that because you opened it from the `/roms/nes` folder, the game must correspond to that system.
### Example 2: The Game Outside the Roms Folder
In this example, the `LittleMedusa_8bitdemo.nes` file is not inside the `retrodeck/roms/nes` folder but in the `download` folder.
When clicked, RetroDECK will prompt a dialog window asking which system the file belongs to and then run it.
### Example 3: Running via CLI
Example full syntax:
`flatpak run net.retrodeck.retrodeck retrodeck/roms/nes/LittleMedusa_8bitdemo.nes`