I see - so the player needs to "drain sheeps" but just not too much so those not become dead. Quite clever and also all themed by with fun. It is like having an adventure but also some strategy building in the same pack.
Some game play improvement ideas here:
- Player would be able to drain sheep until it has a minimum amount of extract left, like; "1hp left sheep".
- Shearer unit; would be the extracter leaving red stuff on the ground, and the collector or player would need to collect these extractions.
- Sheeps would have progress bar on top of them when player attempt to drain those.
- Too easy/too hard to defend if enemies comes always in waves - there could appear some random enemies between waves.
- Shooted projectiles homing toward enemies a bit - from this perspective quite hard to aim direct shots now.
- Only one sheep player can drain at the time; now player may drain 2 or more not equal extraction having sheeps around and some of those others might get dead.
- Turrets could be using ammunition and would be reloaded by shooting them with player projectiles (or by player assistance units).
- Drained sheep corpses could be able to revive within a revival time.
- Player could be able to setup building foundations for sheep/Tower/collector units etc. and insert extraction in those to finish the build while builder units could be help-doing that too, since now player can be only deploying new unit or shooting etc. but not the both.