>>brayth+(OP)
MDL looks really interesting. Is there any similar modern-day language for more advanced (graphically and input wise) adventure games? Because if not I might build one...
>>traes+4E
In the ‘90s (?), LucasArts and Sierra both developed VMs for graphical adventure games (SCUMM and AGI); you can look into languages targetting those.
Inform is a more modern language for text adventures.
Ink is an open-source embeddable language for dialog trees and story puzzles. You’ll need to bring your own game engine, but there’s a Unity3d plugin to help.