You play with the mouse! The interface is very simple. There are two commands, look (the pointer turns into a pair of eyes) and interact (the pointer turns into a hand). To switch between them just press the right mouse button. When you move the mouse over a «sensitive» object the pointer changes shape and, pressing the left button, you get the effect you want. With the eyes selected you get a description of the object (e.g.: «that's a very nice guitar»); with the hand selected you interact with it: if it is something you can pick up it will be picked up, if it can be opened it will be opened, if it is a person you will talk to them... and if there is nothing to be done you get a discouraging message (e.g.: «not a great idea»). To make it clear what you are pointing at, a bar at the bottom centre of the screen shows the name of the object under the pointer (e.g. «guitar»).
When you talk to a character, the lines you can say appear at the bottom of the screen. Pick the one that seems most appropriate by clicking it with the left button.
As you move the pointer around the screen it may turn into an arrow — over a door, for instance: click the left button in that state and you change location, moving to the room next door.
There is also a small map icon in the bottom left corner: click it and a map of the available locations appears, so you can travel straight to the one you want.
In the bottom right corner there are two icons. One is a backpack — the inventory, everything you have collected. The other is a floppy disk, for saving the game, loading a save or quitting back to Windows.
As for the inventory: select the backpack and a panel appears with everything you have picked up. You can look at the items (using the eyes) or take one in hand (clicking it with the arrow). Once an item is in hand the pointer takes its shape. At that point you can leave the inventory with the OK button and use the item wherever you see fit (e.g. use the key on the door). To turn the pointer back into eyes or hand, just press the right button. You can also combine inventory items with each other (e.g. put the battery in the remote control).
If all this sounds complicated (don't worry, it's easy!) there is a tutorial in the main menu where you can practise with the controls.