Very good use of controls / perspective to make an R.T.S. that feels like it fits on the gameboy, which I wouldn't have thought was possible, so major kudos there.
The player could use more feedback on enemies and damage (who is doing damage to who, how much health do buildings / units have) especially if you want to have multiple buildings on the go.
Craters are a good start, but definitely more could be gained from the idea of using the surrounding geography to make decisions on where to put buildings.