Once you use an object, it magically disappears from your inventory. If a scene can be exited in a particular direction, then the mouse cursor changes to an arrow near the edge of the screen. If you click on an inventory object, the cursor changes to that object, and you can attempt to use it on something else by clicking elsewhere. Clicking the correct 'hot spots' on the screen will cause something to happen, or will give you a close-up of an item to manipulate. This is my biggest gripe with the game.
Many scenes are quite detailed, containing lots of tiny objects.
There are workbenches littered with junk, drawers full of old fasteners, boxes of useless mechanical parts, nearly invisible switches etc. It's a common problem with this sort of interface, but that doesn't make it any better. The Atmosphere Like Myst, Lighthouse consists of many fixed, interconnected, and beautifully drawn scenes. All scenes from a given area typically share a design theme, which is echoed repeatedly. You will also repair and pilot a mechanical bat and an ornithopter.