I don't know if you've experienced it yourself or have heard other reports of it, but after playing your game for a few hours last night I've been experiencing a 2048-flavored "tetris effect" all day today. My brain keeps on trying to identify "like things" to collapse together; pretty wild.
I had this a lot while developing 2048. At some point, I'd feel like I could collapse letters while typing, and that's when I decided I should probably stop playing so often.
Assuming you mean all fonts everywhere, I got that too. I thought the next website I looked at went through some kind of redesign until I realized that the next two websites I looked at also looked like that.
I played for about 2 hours right before bed and couldn't get to sleep for hours. I was wired. Don't know if this is related to what you're suggesting or not, but I won't be playing this game again at night time.
I used to get that with other games such as Amplitude on the PS2. I'd close my eyes and my brain could see the game being played with incredible detail. It's happened to me with other games also. I think of it as a type of mental burn in. Goes away after a while.
EDIT: This AI is a better player than me.