Very interesting core mechanic, really simple, perfect little mobile game :)
On level design, I understand the care for being the most accessible possible by providing a succession of reaaaaaaly easy levels, but I felt like it was too much, and it can lead some players to be bored soon
First it was time to understand the mechanics, in level 3 I got it, a little more understanding about the use of numbers came only in level 12 (13rd is a good one too for this) but most of the levels inbetween are too similar and don't add anything more to the understanding of the game
So the challenge I met was only at level 24 ! And there I said to myself ("Oh, this game looks interesting")
level 32 was a good one too !
I stop playing the demo for tonight, but I'm curious of playing the full game soon !