Dang, getting old here...
Just wanted to point out when playing for some time, the game considerably slows down (browser version, around stage 25)
I gave up myself on level 50 since the game was around 1.5fps at this point...
Little tip for higher numbers (ex. 163) : Reach around 20-30 under the target number by multiplying stuff and adding some numbers, and then figure out what chain of numbers to add in order to fill the remaining gap. Seems to work pretty good for me...