Everything must be in balance. Unfortunately, this game, regardless of its name, doesn't know what it means...

It's about:

• "add" and "sub" math operations with single- and two-digit numbers (pos. and neg.);
  
• getting a particular number in the end of the row (or interdependent rows).

Why you should play this:

• you like math and calculations;
  
• fair amount of levels (16 and + 4 more if you are lucky) with increasing difficulty;
  
• puzzles sometimes hard, but always manageable.

Why you may not like it:

• soundtrack - it doesn't fit at all, it's not exactly bad, it just distracts and irritates: complete miss with calm and meditative nature of the game;
  
• bug with 4 additional levels (at least for me) and it doesn't look like devs care about it.

Fair enough to say that devs forgot about balance: soundtrack doesn't fit, there's a chance that additional levels may not be available, gameplay can be considered as an actual gameplay only by ones who love math - pretty unbalanced outcome.