diff --git a/Arch.md b/Arch.md
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+- Use ECS?
+
+- World
+- Creatures
+    - Human
+    - Animal
+    - Monster
+- Sites
+    - Towns
+    - Dungeons
+    - Caves
+    - Ruins
+    - Tavern
+- Items
+    - Weapons
+    - Armor
+    - Food
+    - Potions
+    - Scrolls
+    - Books
+    - Gems
+    - Artifacts
+
+
+- Creatures need agency
+    - Need to be able to move around
+    - Need to be able to interact with the world
+    - Need to be able to interact with other creatures
+    - Need to be able to interact with items
+    - Need to be able to interact with sites
+    - Need an inventory
+- Sites
+    - Need an inventory
+- Items
+    - Need to know their history
+
+
+## Step System
+
+- For each creature
+    - create clone
+    - run creature step
+        - return list of actions
+    - run actions
+    - update creature
+    
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diff --git a/src/game.rs b/src/game.rs
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+use crate::state::GameState;
+
+/**
+ * This is the main game struct.
+ * It takes care of stepping the game forward.
+ * Changes are made to the state struct through the step function.
+ */
+pub struct Game {
+    pub state: GameState,
+}
+
+impl Game {
+    pub fn new(state: GameState) -> Game {
+        Game {
+            state: state,
+        }
+    }
+
+    pub fn step(&mut self) {
+        // get list of all people ids
+        let ids: Vec<u32> = self.state.people.keys().map(|id| *id).collect();
+
+        // step each person
+        for id in ids {
+            let person = self.state.people.get_mut(&id);
+            match person {
+                Some(p) => {
+                    let mut p = p.clone();
+                    p.step(&mut self.state);
+                    self.state.people.insert(id, p);
+                },
+                // person is dead
+                None => (),
+            }
+
+        }
+        // increment time
+        self.state.time.time += 1;
+    }
+
+}
+
+#[cfg(test)]
+mod tests {
+
+    use crate::world::World;
+
+    use super::*;
+
+    #[test]
+    fn test_step() {
+        let state = GameState::new(World::new(100));
+        let mut game = Game::new(state);
+        game.step();
+        assert_eq!(game.state.time.time, 1);
+    }
+
+}
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