Restrict RtSim ships to airships

CHANGELOG.md

@@ -97,6 +97,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Lantern color changes when swapping lanterns
 - NPCs no longer wander off cliffs
 - Guards will defend villagers instead of simply threatening the attacker
+- Seafaring ships no longer spawn on dry land
 
 ## [0.11.0] - 2021-09-11
 

common/src/comp/body/ship.rs

@@ -16,6 +16,8 @@ pub const ALL_BODIES: [Body; 4] = [
     Body::Galleon,
 ];
 
+pub const ALL_AIRSHIPS: [Body; 2] = [Body::DefaultAirship, Body::AirBalloon];
+
 make_case_elim!(
     body,
     #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
@@ -41,6 +43,10 @@ impl Body {
 
     pub fn random_with(rng: &mut impl rand::Rng) -> Self { *(&ALL_BODIES).choose(rng).unwrap() }
 
+    pub fn random_airship_with(rng: &mut impl rand::Rng) -> Self {
+        *(&ALL_AIRSHIPS).choose(rng).unwrap()
+    }
+
     /// Return the structure manifest that this ship uses. `None` means that it
     /// should be derived from the collider.
     pub fn manifest_entry(&self) -> Option<&'static str> {

server/src/rtsim/entity.rs

@@ -69,7 +69,9 @@ impl Entity {
             RtSimEntityKind::Random => {
                 match self.rng(PERM_GENUS).gen::<f32>() {
                     // we want 5% airships, 45% birds, 50% humans
-                    x if x < 0.05 => comp::ship::Body::random_with(&mut self.rng(PERM_BODY)).into(),
+                    x if x < 0.05 => {
+                        comp::ship::Body::random_airship_with(&mut self.rng(PERM_BODY)).into()
+                    },
                     x if x < 0.45 => {
                         let species = *BIRD_MEDIUM_ROSTER
                             .choose(&mut self.rng(PERM_SPECIES))