Waste of money, unfortunately

Good grief this is bad. I love tower defense games, particularly RPG-based ones, but here the RPG elements are way over-blown (virtually non-existent); in-app purchases are not a luxury but a requirement (bad form for a paid app); and there are extremely limited strategic options for a modern tower defense game.

Save your money for any one of the many, many better tower defense games currently on the market.

Abradax about Royal Defense: Invisible Threat