Thanks for the kind feedback! Yes, the idea is that initially, countdown is the most powerful strategy (gives you multiplier for the number of tiles in your chain) but eventually the artifacts and items catch up or surpass it in terms of strategy, at least that is the idea. The +1/-1 and the items are supposed to help you get that chain, or work around your strategy.
Agree on the color scheme and general readability, I didn't put much thought in these but turned out to be essential (moved away from a single color gradient since consecutive colors tended to be very similar, but the alternative didn't quite work either).