Could be better
A few other things that bug me about the game: when choosing to double the reward to GET more strawberry upgrade material, the reward is only 20% of the original, which is super frustrating, plus when it's time to stop the sliding thing at the bottom after the ad, more than half the time, when you click stop, the slider immediately jumps to the far left @ 1x. So now I've watched another stupid ad for basically nothing. If I never see another Whiteout Survival ad in my life, I will be a happy camper. The shop's availability of berries for gems is RIDICULOUSLY OVERPRICED. Seriously, you need to change it.
How about little potions or something to be able to rearrange the board with fresh tiles? Or perhaps a resurrection item? What's your plan for maxed out monsters - will anything convert to something usable?