SLT Retro is a new theme for your Smart Launcher.
Of course you need Smart Launcher in order yo use it, you can install it from here:
https://play.google.com/store/apps/details?id=ginlemon.flowerfree
To apply this theme, open Smart Launcher → Preferences → Themes, then select Retro
Enjoy it :)</br></br></br></br></br></br></br>