First of all this app does not tell you that it costs money. Yes, the app is free to download, but where most apps would say "in app purchases", this one makes you buy a subscription on their website so they dont have to say that (its outside the app). The fact that they are not up front about them only giving you a few slides and you have to subscribe for the rest is just sneaky and underhanded.
Wizardraghnall about Spine Decide, v5.1.1