On one end of the spectrum:
I could lay it all out on the table, images of all the different characters and enemies, thier names, what they do, etc.
All the places you can visit, so on and so forth.
The Good: People would know how much is in the game
The Bad: People won't have any big suprises
And on the other end of the spectrum:
I list very little, only the main characters, and ommiting the final boss, and being very short and mysterious about what they do. And only cover the coarse places you can go, with no big details.
The Good: People will have lots of suprises and discoveries in-game
The Bad: People may think there is nothing worth doing in the game, and not buy it.
So what do you think? I need some serious feedback, this is a massive decision =/
