Most levels can be completed without spending any money, although the more powerful weapons and items can only be purchased by spending real money on in - game money and gold. (the-games-blog.com)
It also features a number of power - ups, which can be bought with in - game currency or acquired more quickly by spending real money on them. (adweek.com)
Don't, however, expect to sit down with it for hours and grind non-stop through the story without spending real money. (indiewatch.net)