Here is a design mockup of the game ui, basicaly done just to get an idea of how it might look.
The ui will consists of 2 main parts.
The Inventory is an expandable 'bar' of inventory items, when you pick up an item it goes into this bar.
Clicking on an item makes you 'hold' the item.
The Radial Menus
The Radial Menus are context-senstive action choices, when you click on somthing in the game world you are presented with a list of actions, such as.
Pretty standard stuff.
Furthermore, if you have an item in-hand it chances the potential list, take this for example:
If you are holding a key and you click on a door, your options are likely to be.
'open door with key'
In this example:
you are holding a crowbar, and you click on a person, your options might be.
'beat man with crowbar'
'give crowbar to man'
pretty standard adventure stuff; the goals for the UI are to make it exceptionally intuitive, graphically appealing, and really contribute to the gameplay (through a wealth of potential options)