Where is the store so you can buy power-ups for Mahjong Sanctuary?

When you click on a new level to play, the first screen that pops up offers ADD for the power ups.  But I do not think they are necessary. I am well over 180 levels and have not even come close to thinking of needing a power up.  Unlike Quinn’s or M. Escape I don’t think I have ever needed more than a half dozen replays to load a winnable layout.

I like the layouts on this game as well. I haven’t repeated too many times to complete the level.