[3JPLW]

The bonds only form with new tiles emerging from the bottom, so it's best to keep the bottom as clear as possible. Also, the timer will skip ahead to a new row if there are no immediate moves left, so it's best to maximize the number of possible moves.

The best strategy I've found is to build two towers on either edge of the board. One tower is reserved for #1-9, and the other side is reserved for 10-19. I aggressively clear the bottom and break any links, and then I optimize the storage of my towers. There's only enough space for stacks 8 high, however, so sometimes I need to make a third stack in the middle (ideally with 9, 10, and 11). I've gotten as high as 20x8 on iOS this way, but it takes some luck.

[icoder]

Interesting! I converged to (almost) the same strategy (I just frantically keep #1-9 at one end (1 column with overshoot to a seconds or third), and #10-19 at the other and try breaking bonds asap). It got me to my first 20.