diff --git a/world/src/sim/mod.rs b/world/src/sim/mod.rs
index a8a78ebc45..5c22d573c4 100644
--- a/world/src/sim/mod.rs
+++ b/world/src/sim/mod.rs
@@ -55,44 +55,37 @@ pub struct WorldSim {
 
 impl WorldSim {
     pub fn generate(mut seed: u32) -> Self {
-        seed = seed_expan::diffuse(seed);
-        let mut gen_seed = |seed: &mut u32| std::mem::replace(seed, seed_expan::diffuse(*seed + 1));
+        let mut seed = &mut seed;
+        let mut gen_seed = || {
+            *seed = seed_expan::diffuse(*seed);
+            *seed
+        };
 
         let mut gen_ctx = GenCtx {
-            turb_x_nz: SuperSimplex::new().set_seed(gen_seed(&mut seed)),
-            turb_y_nz: SuperSimplex::new().set_seed(gen_seed(&mut seed)),
-            chaos_nz: RidgedMulti::new()
-                .set_octaves(7)
-                .set_seed(gen_seed(&mut seed)),
-            hill_nz: SuperSimplex::new().set_seed(gen_seed(&mut seed)),
+            turb_x_nz: SuperSimplex::new().set_seed(gen_seed()),
+            turb_y_nz: SuperSimplex::new().set_seed(gen_seed()),
+            chaos_nz: RidgedMulti::new().set_octaves(7).set_seed(gen_seed()),
+            hill_nz: SuperSimplex::new().set_seed(gen_seed()),
             alt_nz: HybridMulti::new()
                 .set_octaves(8)
                 .set_persistence(0.1)
-                .set_seed(gen_seed(&mut seed)),
-            temp_nz: SuperSimplex::new().set_seed(gen_seed(&mut seed)),
-            dry_nz: BasicMulti::new().set_seed(gen_seed(&mut seed)),
-            small_nz: BasicMulti::new()
-                .set_octaves(2)
-                .set_seed(gen_seed(&mut seed)),
-            rock_nz: HybridMulti::new()
-                .set_persistence(0.3)
-                .set_seed(gen_seed(&mut seed)),
-            cliff_nz: HybridMulti::new()
-                .set_persistence(0.3)
-                .set_seed(gen_seed(&mut seed)),
-            warp_nz: BasicMulti::new()
-                .set_octaves(3)
-                .set_seed(gen_seed(&mut seed)),
+                .set_seed(gen_seed()),
+            temp_nz: SuperSimplex::new().set_seed(gen_seed()),
+            dry_nz: BasicMulti::new().set_seed(gen_seed()),
+            small_nz: BasicMulti::new().set_octaves(2).set_seed(gen_seed()),
+            rock_nz: HybridMulti::new().set_persistence(0.3).set_seed(gen_seed()),
+            cliff_nz: HybridMulti::new().set_persistence(0.3).set_seed(gen_seed()),
+            warp_nz: BasicMulti::new().set_octaves(3).set_seed(gen_seed()),
             tree_nz: BasicMulti::new()
                 .set_octaves(12)
                 .set_persistence(0.75)
-                .set_seed(gen_seed(&mut seed)),
-            cave_0_nz: SuperSimplex::new().set_seed(gen_seed(&mut seed)),
-            cave_1_nz: SuperSimplex::new().set_seed(gen_seed(&mut seed)),
+                .set_seed(gen_seed()),
+            cave_0_nz: SuperSimplex::new().set_seed(gen_seed()),
+            cave_1_nz: SuperSimplex::new().set_seed(gen_seed()),
 
-            structure_gen: StructureGen2d::new(gen_seed(&mut seed), 32, 24),
-            region_gen: StructureGen2d::new(gen_seed(&mut seed), 400, 96),
-            cliff_gen: StructureGen2d::new(gen_seed(&mut seed), 80, 56),
+            structure_gen: StructureGen2d::new(gen_seed(), 32, 24),
+            region_gen: StructureGen2d::new(gen_seed(), 400, 96),
+            cliff_gen: StructureGen2d::new(gen_seed(), 80, 56),
         };
 
         let mut chunks = Vec::new();
@@ -103,11 +96,11 @@ impl WorldSim {
         }
 
         let mut this = Self {
-            seed,
+            seed: *seed,
             chunks,
             locations: Vec::new(),
             gen_ctx,
-            rng: ChaChaRng::from_seed(seed_expan::rng_state(seed)),
+            rng: ChaChaRng::from_seed(seed_expan::rng_state(*seed)),
         };
 
         this.seed_elements();