It's a port of the original Super Mario Bros from the NES to the Game Boy Color. The physics feel very nice, and I like how the sprites are adapted.
The port also extends the game. After the 8 original worlds, Quest B adds 8 more with new enemies, mechanics, and even bosses! I had so much fun playing it.
Also, the game is FOSS: https://github.com/Mico27/SuperMarioBrosMini
Kind of a strange thing to make, since Super Mario Bros. Deluxe is already on the GBC. Good if you want to see the whole screen at once, I suppose.
This version is way better, in my opinion. Not only the sprite size, but these 8 additional levels are very fun.
I missed that the 8 additional levels are new. I'll have to check it out sometime!