Questions about engine possibilities

[goamanu]

@Jinix, thank you for your advice.
It's all about time and money, as usual. I cannot afford to spend a huge amount of money on a sophisticated game engine, that requires a lot of time to be masterred.
I want to do it all by myself. HPL engine seemed to be the perfect compromise, 'cause I liked the phisycs and the relatively easy scripting. The best thing is that HPL is used in an half-adventure game and it has the adventure elements: contraptions, inventory, letters, etc.
My only two concerns are related to stand-alone capability (under copyright) and scripting limitations. Very few adventure games have moving trees and grass, for example. Even today, the majority of AG's are bidimensional, which is a shame
A lighter environment and puzzle ability would be great!