I'm not sure exactly how a green lantern ring works...
 
It can create anything you can imagine, right?
 
Wouldn't it be possible for me to imagine a button that kills all my enemies then just press it?  What's the deal?  What are the limitations?

They each depend on emotions, green for example works only for Willpower, so you would have to bring up enough willpower to "Kill all your enemies" which would be more than anyone has.

" They each depend on emotions, green for example works only for Willpower, so you would have to bring up enough willpower to "Kill all your enemies" which would be more than anyone has. "

Each Ring is Fueled by a different emotion/state of being.
 
Green - Will
Yellow - Fear
Red - Rage
Blue - Hope
Sapphire - Love
Indigo - Compassion
Orange - Avarice (greed)
Black - Death
White - Life
 
as for the button thing, you couldn't do it because the Constructs don't have the power to just take life. It's hard to explain, the constructs as far as I know need to physically touch their targets whether is be a blast, saw, a fist, a bat or whatever. It can't just say die and everybody die. And up until the Sinestro Corps War the Green Lanterns were not authorized to use deadly force. Though they can now.

" Each Ring is Fueled by a different emotion/state of being.  Green - Will Yellow - Fear Red - Rage Blue - Hope Sapphire - Love Indigo - Compassion Orange - Avarice (greed) Black - Death White - Life  as for the button thing, you couldn't do it because the Constructs don't have the power to just take life. It's hard to explain, the constructs as far as I know need to physically touch their targets whether is be a blast, saw, a fist, a bat or whatever. It can't just say die and everybody die. And up until the Sinestro Corps War the Green Lanterns were not authorized to use deadly force. Though they can now. "

" @Caligula said:

" Each Ring is Fueled by a different emotion/state of being.  Green - Will Yellow - Fear Red - Rage Blue - Hope Sapphire - Love Indigo - Compassion Orange - Avarice (greed) Black - Death White - Life  as for the button thing, you couldn't do it because the Constructs don't have the power to just take life. It's hard to explain, the constructs as far as I know need to physically touch their targets whether is be a blast, saw, a fist, a bat or whatever. It can't just say die and everybody die. And up until the Sinestro Corps War the Green Lanterns were not authorized to use deadly force. Though they can now. "

how about i imagine a gun and the bullets can instantly kill anyone. "

Imagination is of course also a factor, thats also the reason why i think Kyle Rayner to be the most potent of the lanterns (being an artist and such)
 
here also two cases of Kyle being able to form a gun construct
 
 http://media.comicvine.com/uploads/6/61378/1450589-05_3_b.jpg
 http://media.comicvine.com/uploads/6/61378/1450605-circle_of_fire_2_31_b.jpg

Well the ring is only limited by your imagination, but to create a construct of a button that kills all your enemies, you'd need to have an understanding of how that it would work. You wouldn't be able to create it because you wouldn't know how to create it. It'd be like you having trouble on a math problem, having access to everything you need to create a TI-83 calculator, and me saying "Why don't you just make a calculator?" Conceivably you could but since you (likely) don't understand how then you won't be able to.
On the subject of the rings place as technology in itself...I always think of this quote in relation to the ring
"Any sufficiently advanced technology is indistinguishable from magic"- Arthur C Clarke