
As other answers have said the first sentence sounds hypothetical. The reason this statement is hypothetical is that the machines being talked about do have energy. With context it might read:



  Of course, all machines are either connected to an electricity supply
  or powered by some other energy source. Machines wouldn't work without
  energy.



The second sentence could either be talking about the future or a present 'habit'. Assuming the idea is to describe a habit that machines have, with context it might read:



  It is common to see machines connected to some kind of power source:
  Machines won't work without energy.



The third sentence is quite similar to the first, this time the emphasis being on hypothetical capability. Machines can function but they only have this capability because of energy.



  Machines are capable of performing amazing tasks but of course they
  need a power source. Machines couldn't work without energy.



The final statement is one of fact about machines' capabilities - true now, true in the past, true always.



  It is impossible for machines to operate unconnected to a power
  supply: Machines can't work without energy.


"wouldn't" vs. "won't" & "couldn't" vs "can't"
I'm in the process of creating a web app. I have many randomly-generated non-player characters in a database. I can pull a lot of information about them - their height, weight, down to eye color, hair color, and hair style.

For this, I am solely interested in generating a graphical representation of the face. Currently the information is displayed with text in the nicest way possible, but I believe it's worth generating these faces for a more... human experience.

Problem is, I don't know where to start. Were it 2007, I'd naturally think to myself that using Flash would be the best choice. I'd love to see "breathing" simulated. However, since Flash is on its way out, I'm not sure of a solid solution.

With a previous game, I simply used layered .PNGs to represent various aspects of the player's body: their armor, the face, the skin color. However, these solutions weren't very dynamic and felt very amateur. I can't go deep into this project feeling like that's an inferior way to present these faces, and I'm certain there's a better way.

Can anyone give some suggestion on how to pull this off well?
