The basic chords in this Acoustic Remix of Fireflies by Owl City Are F5 C5 A5 D5 G5

F5            C5        
You would not believe your eyes
G5                      A5   x2
If ten million fireflies lit up the world as i fell asleep
'Cause they'd fill the open air
And leave teardrops everywhere
You'd think me rude but I'd just stand and stare
 
Repeat through every verse

[Chorus:]

F5              C5               G5
I'd like to make myself believe
F5                C5     G5      A5
That planet Earth turns slowly
F5               C5              G5        A5
It's hard to say that I'd rather stay awake when I'm asleep
F5                   C5          D5       
'Cause everything is never as it seems

'Cause I'd get a thousand hugs from ten thousand lightning bugs
As they tried to teach me how to dance
A foxtrot above my head
A sockhop beneath my bed
A disco ball is just hanging by a thread

[Repeat Chorus]