Very Zen Mental Math Machine

So many math challenge apps have a clunky, dysfunctional user interface. The Very Zen Mental Math Machine aims to fix that, and throws addition, subtraction, multiplication, and division challenges at you without any distractions.

Features:
* 5 difficulty settings
* Fluid, pleasant, and distraction-free user interface
* Dark and light solarized themes

Open-source at https://github.com/Ohmnivore/ZenMathMachine