Its a good game, but its too short, a bit imbalanced.
First of all, you should double ALL the content, including quests, gameplay place and upgrades count.
Second, you've put a sea part, but didnt used it as well much, only once.
Third, add sea and air! It would be fun!
Next one, you should add more objects, more then stone, maybe lava and water, maybe other interactive elements.
And of course, making diamond stuff so op is stupid. Like best cooldown does not work anymore, leaving you to digg for diamonds quickly.
Just double the fun. Such a pleasure should rest longer.