It’s hard to describe the seductive power of Abyss Attack’s visual design, but its deep waters can only be eclipsed by the breadth of one’s imagination.
Abyss Attack can get repetitive since you'll earn crystals for the shop at a snail's pace, but great controls and a unique visual style still make it an enjoyable shooter.
The controls are great and the setting, graphics and sound are unique, but this is also an example of what’s wrong with the IAP model: developers need to ensure that the player feels like their time investment is worthwhile. Only then will that player feel like they want to spend a little of their real money on in-app purchases.