Nice work! kept playing because i wanted to further expand my base. I like how you can chose to move away from your crystal to mine some resource by hand but always have to be aware of ghosts in your base.
Some strategy elements except that ghosts only go for the crystal and not the other buildings, so there is no real strategy in placing them, once you placed them you dont need to look at them again.
Would be fun to add some tower defense elements, like placing storage's to form a certain maze so ghosts have to follow a specific path :)
It took me some time to create the first tower that would auto attack ghosts. I would have liked a basic tower from the start. Other than that it kept me playing for a while. Good job!