Plenty of games are being written in C for the Game Boy on a regular basis. Just a few polished examples of that: https://tangramgames.itch.io/tobu-tobu-girl-d

Plenty of games are being written in C for the Game Boy on a regular basis. Just a few polished examples of that: https://tangramgames.itch.io/tobu-tobu-girl-deluxe https://tangramgames.itch.io/tobu-tobu-girl-deluxe https://user0x7f.itch.io/black-castle https://user0x7f.itch.io/black-castle https://binji.itch.io/porklikegb https://binji.itch.io/porklikegb https://pocketpixel.design/super-jetpak-dx-game-boy-rom.html https://pocketpixel.design/super-jetpak-dx-game-boy-rom.html https://aiguanachein.itch.io/powa https://aiguanachein.itch.io/powa https://thegreatgallus.itch.io/cavern-mvm-9 https://thegreatgallus.itch.io/cavern-mvm-9 https://user0x7f.itch.io/gunship https://user0x7f.itch.io/gunship https://www.infinitygbc.com/ https://www.infinitygbc.com/ ASM will tend to be more efficient, especially if written by someone with experience and skill, but that isn't enough to prevent other tools from being used successfully. It's described in much more detail in the linked article.