A lot of fun, and more effective than i was expecting. After losing some numbers and getting worse at math, by the end of the final round I had resorted to just adding 2s and 4s. Later, I was describing it to someone who suggested that 7 + 7 + 2 =16 wouldn't have been too difficult.
Oh yeah? On round one, sure, that's an easy play. By the end of the last round? No, that was beyond me!
...and I really wasn't expecting that.