or, cross sums- if one is a loser. Sersiously addictive, in fact this past week or two ive let go of invasive and rude sudoko and cage sudoko to be happily subsumed by kakuro. imo the biggest benefit is its stimulating enough you feel challenged, accomplished, not bored but not like social media where u are overhwelmed with info. many amazing conclusions i have made while embroiled in a battle of soul and spirit on the kakuro plains.highly recommend, nerds