well its just to put a name, im thinking on instead of wait the special blocks to appear create them, but i think its too far for a gameplay change so this idea can became a new feature.
so here it is: If you conect 3 they explode and become resources right?, but theres nothing "special" when you explode 4 or more, maybe 4 its just a simple number so 5 its more dificult to make... i mean: Make a line of 5 and the block in the middle will became a super block or diamond that will multiply (x2,3... whatever) the line where its included.
An example, you have your blocks and make a fire line of 5 in the middle of the screen(horizontally), then it creates a Red Diamond, then another line explodes (with x2 drawing) and after that a fire block falls (also you put another fire block under the diamond while exploding) creating a 3-vertical.line block (with the diamond in the middle) then it explodes with a x3...adding the effect of the Red Diamond of x2
So you can collect diamonds, or make them stronger (placing in the middle of another line of 5 blocks) to get more resources.
That would get more resources ,a lot in my point of view, so maybe weekly events or daily events or little challenges (or attacks to your ...map?) that if missed or losed will steal or destroy your resources and/or crystals.
It would be neat if the game had different play modes. I like the one now, and would hate to see it be gone in a future update, but would welcome new options of play or new areas of the world to do similar things.