It's a nice puzzler. I'm not quite sure though what makes this one stand out for people, while similarly accomplished titles often go unnoticed. Possibly simply a little hype generation. That said, this is still an easy recommendation if it looks like your type of thing.
IAP is present. The important stuff can be unlocked through play, though I cannot yet say at what rate, and have to question if the decision to have only the one mode unlocked from the start was driven by desire for optimal player experience. Some cosmetic options (tile sets) can only be bought with more money.