The game's barter system will allow you to purchase fuses to complete various puzzles throughout your quest. Without completing them, you can't proceed. But there's a major loophole in the system, starting with the very first fuse puzzle. After completing it, go back to the puzzle and grab all of the fuses. These will stay in your inventory and can be used on future puzzles, eliminating the necessary barter purchase for more fuses at a future date. You'll never have to search for or purchase more fuses if you do this!