Hi just played the game.
I like the theme of the game, it very unique and makes it stand out. Traveling around the world collecting stamps sound very relaxing.
The gameplay is very simplistic, if a bit repetitive. With some more work on the gameplay, it could become a solid mobile-game actually.
Regarding graphics, some parallax scrolling on the backgrounds and the plane rotating in the direction it's going would greatly improve the game.
I can tell that the game is quite complete, which is a shame since there's a lot of potential in this one.