Using Diamonds, I unlocked the 8x Speed Boost. I had some left over so I unlocked the 2x boost as well, however there was no increase with that purchase, but my 20 diamonds were taken. Please fix this.
I would like to see the achievements organized in a more meaningful way. Currently, the player has to scroll through them all and it can be a little difficult to find one that should be pursued next. The majority of the achievements are just advanced levels of a basic activity or goal. Combining them so that it shows only the next step in the achievement branch, will make them simpler to navigate.
My wording is a little confusing, but I hope you get the idea.
The game is good. I play mostly for the badges though. The sound effects not being turned off when disabling sound is annoying but other then that the game is well done.