Thanks a lot :) .
Yeah, the objective is, in general, to get the least tiles remaining in the least turns. It's literally impossible to clear the board because at most you could possibly have an arrow move the last remaining block to destroy itself, but then you'd still have that numbered block. That's why there's also the more tangible objectives of getting below 200 and below 50% each board, besides the goal of seeking the best lowest score.
Because you want arrows remaining if you still need to move blocks(though can also be the best source to reduce your score), and the different blocks have different values, there's more layers of depth available to you after you play more than just trying to remove any block.