When I chose "full screen" in Enigma on my new computer the display is full screen but because the monitor is "HD" the cells are not square. (the poor marble looks like an egg)
Set your HD screen to not stretch the image to fit the screen. :-)
I can do that on mine. It would also happen to videos, btw.
But yes, native widescreen support needs to be discussed for enigma.
However, since many of the levels are designed in a way that you are not expected to see certain parts of the level too early, I doubt it will be sensibly possible to do much except adding a background image frame.
I think this subject has come up before, and it has been discussed if it is possible to move the inventory to the right or left, at which point the gamefield would fit on a 16:10 or 16:9 screen much better. However, the inventory is also used to display text messages, which doesn't work well vertically...