Trim is similar to the concept of bouyancy. If the ether ship is not kept level or trim, it flounders in the ether and falls into a nearby planet. You guide your ship by the constellations with charts included in the game. Over 500 objects, some unique and others common, are sold at Alchemists, Pawn Shops and the like. Many towns have archaeologists who'll identify the use and value of objects and artifacts, and you can sell items at the Pawn Shop.
Inventions are often essential to completing part of the main plot or mini-quests.
The water breather and mineral detector are particularly ingenious inventions, amusing and useful at the same time. The keyboard interface is quite sophisticated for object manipulation, and I found it easiest and fastest. Combining keyboard commands with the mouse or joystic accelerates the action to light speed. The inventory is limited to 21 items that you can carry at one time. You must be careful not to discard or abandon essential and unique items or you will have to restore an earlier save game or start the game over.