I first played this game back when it was on the Sega Master, then it got an upgrade to the TurboGrafx 16 , I'm 68 years old now, have owned most all the old game consoles and and still play old games on the Android with emulators.
Needless to say, I'm glad I found GoG and this game, I love it a lot and I'm one of those that plays the games I like over and over again... Even after all these years.
The only thing I miss from your game is the original charm stones and the Karma requred with different armor in order to get better armor. It made the game more challenging as some gear was harder to get.
I thought this would affect me, but the game is so over whelmingly well made with the great graphics and music upgrade, it doesn't seem to matter much.
My hats off to you Wonderboy Devs!
What are you working on next? Maybe Sega Genesis Wonderboy in Monster World?

Same here I was satisfied with it as a fan of the original since I was a kid. Also played it a lot on GG.
I've also enjoyed the fan remake from 2008, Dragon's Curse Remake, which I think inspired the challenge areas in this one. That one is much harder and has a different world layout however.

You'll have more success contacting the devs over at Steam.