Starts out nice but gets irritating quickly. The space used to display equations must be very small as ones shown with more detailed operations tend to see the text squished together or overlapping, which means you slow down to decipher them and boom you're out of time - even the buyable extra time isn't enough. Doubt I'll ever get beyond Medium difficulty equations.

And yes, as another reviewer says, this most definitely is an asset flip of a free browser game...so go play that instead and don't give whoever uploaded this your hard earned money.