The engine I used is called GBStudio, created by Chris Maltby and you can actually download it for free on itch.io here: https://chrismaltby.itch.io/gb-studio
I highly recommend it! I do not particularly like programming so the engine itself is quite lightweight and easy to pick up. Of course there are restrictions but I quite like the ability to use monochromatic palettes and be able to play it on mobile so I played around with it and made a VN, dress-up game and RPG haha.
You can even port the games you made to emulator or even on physical cartridges which is pretty cool. I say, ONE OF US, give it a try! ^^
Also thank you for your kind words ^^