This game is getting a lot of crap for being too close to Binding of Isaac. To be fair, it does resemble Binding of Isaac a lot, a keyboard, top-down shooter with accumulation of items and perks. The mechanics differ enough to give this game an entirely differnet backbone, though, and let it be said that Avidly Wild games did not rip off Edmund Macmillan in any way, shape, or form.
That being said, though this gives some pretty good Binding of Isaac type gameplay, whether it helps the addicts who are weaning themselves off that famous game remains to be seen. Our Darker Purpose's art style is, in my humble opinion, far more beautiful and intriguing than Isaac's quirky and humorous one, and the music in this game is subtle yet stellar, offering a nice, edgy background to the game's ominous atmosphere.
The lore in Our Darker Purpose is uniquely amazing. Binding of Isaac came with tons of items and an allegory within a story, but it's story is hardly as good, interesting, or compelling as that found in Our Darker Purpose. Many words went into the lore of this game and for that, Avidly Wild, I applaud you. Cordy is a character one can sympathize for, have fun with, and imagine a backstory for in the dark orphanage she lives in. The fragments about bosses, items, and Edgewood are equally fun to read, and all offer a dark humor that is quite well done.
Our Darker Purpose adds more choice than Isaac as well. Isaac's customization had two options: yes or no. You took the item, or you didn't. In this game, the perks and items are a bit more varied and a bit more easier to alter. Arguably, Our Darker Purpose is more user-friendly and easier in that sense. The wiggle room allowed by its choice of perks upon level up and its item stores allow one to build up Cordy in a more specific and designed manner than Binding of Isaac.
Now that I've said everything it has over Binding of Isaac, let me warn you about what NOT to expect from this game. Many people fell in love with the sobbing little boy sitting on poop because of the game's learning curve and skill requirements. You had to be fast on your fingers, or else the unforgiving monsters of the basement would get you. In Our Darker Purpose, however, speed and reaction time is less important. Cordy, though she moves smoothly as of the most recent update, will never hit the speed of Isaac with speed-ups, Wooden Spoon, and the Belt. Though this might seem like it makes the game easier, the enemies in this game are far more advanced, difficult, and tankier than those in Binding of Isaac. This game prioritizes thought over reaction time, and you'll find yourself frustrated not because you didn't tap down fast enough, but because you didn't think to roll at the right time.
TL;DR: Our Darker Purpose has the same surface mechanics as Binding of Isaac, but a deeper story, fresh graphics, and an entirely new item customization system. While it will never replace the mad speed dashing and the crazy bullet and fly frenzies in Binding of Isaac, it offers a new dimension of thought and planning while in the midst of combat. It is definitely worth looking at and getting if the abovementioned bonuses are attractive.