Good premise, I think. Regular and homing rocks feel too powerful in the beginning and for a while after, while the damage field doesn't feel like it scales well.
Feels odd that hunger drains faster than thirst in the desert during both day and night. Suggest making them day/night dependent (lose thirst faster during day, lose hunger faster during night).
Didn't get far enough to see if these are already covered by upgrades, but arrows/mini-map pointing towards items and food would help. (The land's flat, right? The character would be able to see plant groups, oases, and mirages in the distance.)