diff --git a/Cargo.lock b/Cargo.lock
index 91ebe45..24b2baa 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -108,6 +108,12 @@ dependencies = [
  "parking_lot",
 ]
 
+[[package]]
+name = "fnv"
+version = "1.0.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3f9eec918d3f24069decb9af1554cad7c880e2da24a9afd88aca000531ab82c1"
+
 [[package]]
 name = "getrandom"
 version = "0.2.8"
@@ -177,6 +183,7 @@ name = "mantle-diver"
 version = "0.1.0"
 dependencies = [
  "egui-sfml",
+ "fnv",
  "hecs",
  "rand",
  "s2dc",
diff --git a/Cargo.toml b/Cargo.toml
index cb4c04a..e1f4fec 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,6 +7,7 @@ edition = "2021"
 
 [dependencies]
 egui-sfml = "0.4.0"
+fnv = "1.0.7"
 hecs = "0.10.1"
 rand = "0.8.5"
 sfml = "0.20.0"
diff --git a/src/game.rs b/src/game.rs
new file mode 100644
index 0000000..16457da
--- /dev/null
+++ b/src/game.rs
@@ -0,0 +1,16 @@
+use crate::{math::WorldPos, world::World};
+
+pub struct GameState {
+    transient: TransientGameState,
+    persistent: PersistentGameState,
+}
+
+/// Transient game state, not saved to disk
+pub struct TransientGameState {
+    camera_offset: WorldPos,
+}
+
+/// Persistent game state, saved to disk
+pub struct PersistentGameState {
+    world: World,
+}
diff --git a/src/main.rs b/src/main.rs
index 96457cc..64262d6 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,5 +1,8 @@
 mod app;
+mod game;
 mod graphics;
+mod math;
+mod world;
 
 use app::App;
 
diff --git a/src/math.rs b/src/math.rs
new file mode 100644
index 0000000..42a0c17
--- /dev/null
+++ b/src/math.rs
@@ -0,0 +1,6 @@
+pub type WorldPosScalar = i32;
+
+pub struct WorldPos {
+    x: WorldPosScalar,
+    y: WorldPosScalar,
+}
diff --git a/src/world.rs b/src/world.rs
new file mode 100644
index 0000000..509c682
--- /dev/null
+++ b/src/world.rs
@@ -0,0 +1,28 @@
+use fnv::FnvHashMap;
+
+type ChunkPosScalar = i16;
+
+#[derive(Hash)]
+struct ChunkPos {
+    x: ChunkPosScalar,
+    y: ChunkPosScalar,
+}
+
+pub struct World {
+    chunks: FnvHashMap<ChunkPos, Chunk>,
+}
+
+const CHUNK_EXTENT: u16 = 256;
+const CHUNK_N_BLOCKS: usize = CHUNK_EXTENT as usize * CHUNK_EXTENT as usize;
+
+type ChunkBlocks = [Block; CHUNK_N_BLOCKS];
+
+pub struct Chunk {
+    blocks: ChunkBlocks,
+}
+
+type BlockId = u16;
+
+pub struct Block {
+    id: BlockId,
+}