That's a valid criticism - I don't know how it could be fixed.

Maybe more colors could be added? Game balance has been really tricky with this game, as changes play out very differently on mobile devices and "real computers."

More colors seems like the obvious way to increase the difficulty as the user levels-up. With only four colors, random play is quite likely to get a match--the odds of a randomly selected tile matching a given tile is going to be 1 in 4.

From a cursory look (my math may be a little off) it seems like the odds of a tile matching at least one of its 4 cardinal-direction neighbors is ~57% (20 of 35 order-independent variations), and the odds of a tile matching 2 or more of its randomly selected neighbors is ~28%. In other words, with just random play you're going to get a match out of every `+` shaped collection of 5 tiles nearly 1/3rd of the time. Factoring the three-in-a row possibility the odds of a match will go up from there. (And since a match will eliminate several tiles of given color, the odds of getting a match on the "chain reaction" must also be quite high.)