diff --git a/src/main.rs b/src/main.rs
index 5d1cff4..baf622d 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,6 +1,7 @@
 use std::{collections::HashMap, io::BufReader, path::PathBuf, time::Duration};
 
-use sim::{definitions::parser::DefinitionParser, Creature, Site, SiteArea, World};
+use sim::definitions::parser::DefinitionParser;
+use sim::prelude::{Creature, Site, SiteArea, World};
 
 pub mod sim;
 
diff --git a/src/sim.rs b/src/sim.rs
index 6990ba8..5a5ee35 100644
--- a/src/sim.rs
+++ b/src/sim.rs
@@ -1,533 +1,17 @@
-use std::{
-    collections::{HashMap, HashSet},
-    fmt::Display,
-    time::Duration,
-};
-
-use serde::{Deserialize, Serialize};
-use types::WorldCoords;
-use uuid::Uuid;
-
-use definitions::{CreatureDef, SiteDef};
+pub mod prelude {
+    pub use super::combat;
+    pub use super::creature::*;
+    pub use super::definitions::*;
+    pub use super::site::*;
+    pub use super::travel_group::*;
+    pub use super::util::*;
+    pub use super::world::*;
+}
 
 pub mod combat;
+pub mod creature;
 pub mod definitions;
-pub mod types;
-
-pub fn roll_d20() -> i8 {
-    fastrand::i8(1..=20)
-}
-
-#[derive(Debug, Default, Serialize, Deserialize)]
-pub struct World {
-    pub sites: Vec<Site>,
-}
-
-impl World {
-    pub fn advance_time(&mut self, time: Duration) {
-        for site in self.sites.iter_mut() {
-            site.advance_time(time);
-        }
-    }
-}
-
-#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash, Serialize, Deserialize)]
-pub struct SiteId(Uuid);
-
-impl SiteId {
-    pub fn generate() -> Self {
-        Self(Uuid::new_v4())
-    }
-}
-
-impl Display for SiteId {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "s-{}", self.0)
-    }
-}
-
-#[derive(Debug, Serialize, Deserialize)]
-pub struct Site {
-    id: SiteId,
-    pub name: String,
-    pub definition: SiteDef,
-    areas: Vec<SiteArea>,
-    accumulated_time: Duration,
-}
-
-impl Site {
-    #[inline]
-    const fn minimum_tick() -> Duration {
-        Duration::from_secs(3600)
-    }
-
-    pub fn new(definition: SiteDef, name: impl Into<String>, areas: Vec<SiteArea>) -> Self {
-        Self {
-            id: SiteId::generate(),
-            definition,
-            name: name.into(),
-            areas,
-            accumulated_time: Duration::default(),
-        }
-    }
-
-    pub fn id(&self) -> SiteId {
-        self.id
-    }
-
-    fn inner_tick(&mut self) {
-        // Maps where creatures are going during patrol
-        let mut patrol_map: HashMap<CreatureId, (usize, usize)> = HashMap::new();
-        let site_size = self.areas.len();
-        for (area_index, area) in self.areas.iter_mut().enumerate() {
-            // Resolve combat per area
-            if let Some(results) = combat::resolve_combat(&area.population, 600) {
-                for attack in results.attacks {
-                    // println!(
-                    //     "{attacker} [{attacker_id}] attacks {target} [{target_id}]: {attack}",
-                    //     attacker = attack.attacker.map_or("Natural causes", |attacker| &area
-                    //         .find_creature(attacker)
-                    //         .unwrap()
-                    //         .definition
-                    //         .name_singular),
-                    //     attacker_id = attack
-                    //         .attacker
-                    //         .map_or("<no id>".into(), |id| id.to_string()),
-                    //     target = area
-                    //         .find_creature(attack.target)
-                    //         .unwrap()
-                    //         .definition
-                    //         .name_singular,
-                    //     target_id = attack.target
-                    // );
-                    if let Some(damage) = attack.damage {
-                        let target = match area
-                            .population
-                            .iter_mut()
-                            .find(|creature| creature.id == attack.target)
-                        {
-                            Some(target) => target,
-                            None => continue,
-                        };
-                        target.state.damage = target.state.damage.saturating_add(damage);
-                    }
-                }
-                for death in results.kills {
-                    area.population
-                        .retain(|creature| creature.id != death.killed);
-                }
-            }
-
-            // Resolve patrolling creatures
-            if site_size > 1 {
-                for creature in area.population.iter() {
-                    if fastrand::f32() < creature.patrol_chance() {
-                        // Make sure the creature patrols to a different area
-                        let target_index = {
-                            // Remove the current area from the range
-                            let index = fastrand::usize(0..site_size - 1);
-                            if index < area_index {
-                                index
-                            } else {
-                                // Skip the current area
-                                index + 1
-                            }
-                        };
-                        patrol_map.insert(creature.id, (area_index, target_index));
-                    }
-                }
-            }
-        }
-
-        if !patrol_map.is_empty() {
-            println!("Patrols:");
-            for (id, (from, to)) in patrol_map.iter() {
-                println!("\t[{id}] patrols [{from}] -> [{to}]")
-            }
-        }
-
-        // Apply patrol map
-        for (creature_id, (from_index, to_index)) in patrol_map {
-            let creature = self
-                .areas
-                .get_mut(from_index)
-                .expect("Patrol: getting the area where the patrolling creature is")
-                .remove_creature(creature_id)
-                .expect("Patrol: finding the creature inside the area");
-            self.areas
-                .get_mut(to_index)
-                .expect("Patrol: getting the area where the creature is moving to")
-                .population
-                .push(creature);
-        }
-
-        println!("Tick! {}", self);
-    }
-
-    pub fn generate_from_def(site_def: &SiteDef) -> Self {
-        Self::new(
-            site_def.clone(),
-            "Gorbo's cave",
-            vec![
-                SiteArea::default();
-                fastrand::usize(site_def.min_size as usize..=site_def.max_size as usize)
-            ],
-        )
-    }
-
-    pub fn areas(&self) -> &Vec<SiteArea> {
-        self.areas.as_ref()
-    }
-
-    pub fn areas_mut(&mut self) -> &mut Vec<SiteArea> {
-        self.areas.as_mut()
-    }
-
-    pub fn populate_randomly(&mut self, creature_defs: &[&CreatureDef]) {
-        let area_count = self.areas.len();
-        {
-            let min_count = area_count;
-            let max_count = (5 + (area_count - 1) * 3).max(min_count);
-            for _ in 0..fastrand::usize(min_count..=max_count) {
-                let area_t = fastrand::f32().powi(2);
-                let index = (area_t * (area_count - 1) as f32).round() as usize;
-                let creature = Creature::generate_from_def(
-                    (*fastrand::choice(creature_defs.iter()).unwrap()).clone(),
-                );
-                self.areas
-                    .get_mut(index)
-                    .expect("Creature generation index for depth is out of bounds")
-                    .population
-                    .push(creature)
-            }
-        }
-    }
-
-    pub fn advance_time(&mut self, time: Duration) {
-        self.accumulated_time += time;
-        while self.accumulated_time >= Self::minimum_tick() {
-            self.inner_tick();
-            self.accumulated_time -= Self::minimum_tick();
-        }
-    }
-
-    /// Finds a creature with given id, removes it from the site and returns it with ownership
-    pub fn remove_creature(&mut self, id: CreatureId) -> Option<Creature> {
-        for area in self.areas.iter_mut() {
-            if let Some(creature) = area.remove_creature(id) {
-                return Some(creature);
-            }
-        }
-        None
-    }
-}
-
-impl Display for Site {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(
-            f,
-            "site \"{name}\" [{id}] [",
-            name = self.name,
-            id = self.id
-        )?;
-        for (index, area) in self.areas.iter().enumerate() {
-            write!(f, "\n\tarea {} [", index)?;
-            for creature in area.population.iter() {
-                write!(f, "\n\t\t{}", creature)?;
-            }
-            if !area.population.is_empty() {
-                write!(f, "\n\t")?;
-            }
-            write!(f, "]")?;
-        }
-        if !self.areas.is_empty() {
-            writeln!(f)?;
-        }
-        write!(f, "]")
-    }
-}
-
-#[derive(Clone, Debug, Default, Serialize, Deserialize)]
-pub struct SiteArea {
-    pub population: Vec<Creature>,
-}
-
-impl SiteArea {
-    pub fn from_creatures(creatures: &[Creature]) -> Self {
-        Self {
-            population: creatures.to_vec(),
-        }
-    }
-
-    pub fn find_creature(&self, id: CreatureId) -> Option<&Creature> {
-        self.population.iter().find(|creature| creature.id == id)
-    }
-
-    pub fn find_creature_mut(&mut self, id: CreatureId) -> Option<&mut Creature> {
-        self.population
-            .iter_mut()
-            .find(|creature| creature.id == id)
-    }
-
-    /// Finds a creature with given id, removes it from the area and returns it with ownership
-    pub fn remove_creature(&mut self, id: CreatureId) -> Option<Creature> {
-        for i in 0..self.population.len() {
-            if self.population[i].id == id {
-                return Some(self.population.swap_remove(i));
-            }
-        }
-        None
-    }
-}
-
-#[derive(Clone, Default, Eq, PartialEq, Hash, Debug, Serialize, Deserialize)]
-pub struct CreatureState {
-    pub damage: i32,
-}
-
-#[derive(Clone, Copy, Eq, PartialEq, Hash, Debug, Serialize, Deserialize)]
-pub struct CreatureId(Uuid);
-
-impl CreatureId {
-    pub fn generate() -> Self {
-        Self(Uuid::new_v4())
-    }
-}
-
-impl Display for CreatureId {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "c-{}", self.0)
-    }
-}
-
-#[derive(Clone, Eq, PartialEq, Hash, Debug, Serialize, Deserialize)]
-pub struct Creature {
-    id: CreatureId,
-    pub definition: CreatureDef,
-    pub state: CreatureState,
-}
-
-impl Creature {
-    pub fn generate_from_def(definition: CreatureDef) -> Self {
-        Self {
-            id: CreatureId::generate(),
-            state: CreatureState::default(),
-            definition,
-        }
-    }
-
-    pub fn id(&self) -> CreatureId {
-        self.id
-    }
-
-    pub fn patrol_chance(&self) -> f32 {
-        if self.definition.patrols {
-            0.5
-        } else {
-            0.0
-        }
-    }
-
-    pub fn health(&self) -> i32 {
-        self.definition.health - self.state.damage
-    }
-
-    pub fn is_alive(&self) -> bool {
-        self.health() > 0
-    }
-}
-
-impl Display for Creature {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(
-            f,
-            "{singular} ({hp}/{max_hp}) [{id}]",
-            singular = self.definition.name_singular,
-            hp = self.health(),
-            max_hp = self.definition.health,
-            id = self.id
-        )
-    }
-}
-
-#[derive(Debug)]
-pub struct KillData {
-    pub killed: CreatureId,
-    pub killer: Option<CreatureId>,
-}
-
-#[derive(Clone, Debug)]
-pub struct Attack {
-    pub to_hit_modifier: i8,
-    pub threat_treshold: i8,
-    pub armor_class: i8,
-}
-
-#[derive(Debug)]
-pub enum AttackResult {
-    CritMiss,
-    Miss,
-    Hit,
-    Crit,
-}
-
-#[derive(Clone, Debug)]
-pub struct AttackRoll {
-    pub attack: Attack,
-    pub roll: i8,
-    pub threat_roll: Option<i8>,
-}
-
-impl AttackRoll {
-    pub fn roll(attack: Attack, roll_fn: fn() -> i8) -> Self {
-        let roll = roll_fn();
-        let mut threat_roll = None;
-        if roll >= attack.threat_treshold {
-            threat_roll = Some(roll_fn());
-        }
-        Self {
-            attack,
-            roll,
-            threat_roll,
-        }
-    }
-
-    pub fn is_crit_miss(&self) -> bool {
-        self.roll == 1
-    }
-
-    pub fn is_auto_hit(&self) -> bool {
-        self.roll == 20
-    }
-
-    pub fn is_hit(&self) -> bool {
-        if self.is_crit_miss() {
-            return false;
-        }
-        if self.is_auto_hit() {
-            return true;
-        }
-        (self.roll + self.attack.to_hit_modifier) >= self.attack.armor_class
-    }
-
-    pub fn is_crit(&self) -> bool {
-        match self.threat_roll {
-            Some(roll) => (roll + self.attack.to_hit_modifier) >= self.attack.armor_class,
-            None => false,
-        }
-    }
-
-    pub fn result(&self) -> AttackResult {
-        if self.is_crit_miss() {
-            return AttackResult::CritMiss;
-        }
-        match self.is_hit() {
-            true => {
-                if self.is_crit() {
-                    AttackResult::Crit
-                } else {
-                    AttackResult::Hit
-                }
-            }
-            false => AttackResult::Miss,
-        }
-    }
-}
-
-#[derive(Debug)]
-pub struct AttackData {
-    pub target: CreatureId,
-    pub attacker: Option<CreatureId>,
-    pub attack_roll: AttackRoll,
-    pub damage: Option<i32>,
-    pub is_deathblow: bool,
-}
-
-impl Display for AttackData {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        if let Some(damage) = self.damage {
-            write!(f, "{damage} damage ")?;
-        }
-        match self.attack_roll.result() {
-            AttackResult::CritMiss => write!(f, "*Critical Miss* ")?,
-            AttackResult::Miss => write!(f, "*Miss* ")?,
-            AttackResult::Crit => write!(f, "!Critical hit! ")?,
-            _ => (),
-        };
-        let mod_symbol = if self.attack_roll.attack.to_hit_modifier >= 0 {
-            '+'
-        } else {
-            '-'
-        };
-        write!(
-            f,
-            ": {total} ({calc_roll} {calc_symbol} {calc_mod}) vs. {ac}",
-            total = self.attack_roll.roll + self.attack_roll.attack.to_hit_modifier,
-            calc_roll = self.attack_roll.roll,
-            calc_symbol = mod_symbol,
-            calc_mod = self.attack_roll.attack.to_hit_modifier.abs(),
-            ac = self.attack_roll.attack.armor_class,
-        )?;
-        write!(
-            f,
-            "{}",
-            if self.is_deathblow {
-                " - Killing blow!"
-            } else {
-                ""
-            }
-        )
-    }
-}
-
-#[derive(Debug)]
-pub struct CombatResults {
-    pub kills: Vec<KillData>,
-    pub attacks: Vec<AttackData>,
-}
-
-#[derive(Debug)]
-struct CombatState {
-    creature: Creature,
-    damage: i32,
-    enemies: HashSet<CreatureId>,
-}
-
-impl CombatState {
-    pub fn is_alive(&self) -> bool {
-        self.damage < self.creature.health()
-    }
-}
-
-impl CombatState {
-    pub fn from_creature(creature: Creature) -> Self {
-        Self {
-            creature,
-            damage: 0,
-            enemies: HashSet::new(),
-        }
-    }
-}
-
-#[derive(Eq, PartialEq, Hash, Debug, Serialize, Deserialize)]
-pub struct TravelGroup {
-    pub creatures: Vec<Creature>,
-    pub position: WorldCoords,
-}
-
-impl TravelGroup {
-    pub fn new(creatures: Vec<Creature>, position: WorldCoords) -> Self {
-        Self {
-            creatures,
-            position,
-        }
-    }
-
-    pub fn insert(&mut self, creature: Creature) {
-        self.creatures.push(creature)
-    }
-
-    pub fn remove(&mut self, id: CreatureId) {
-        self.creatures.retain(|creature| creature.id != id);
-    }
-}
+pub mod site;
+pub mod travel_group;
+pub mod util;
+pub mod world;
diff --git a/src/sim/combat.rs b/src/sim/combat.rs
index eaa56e4..bb76894 100644
--- a/src/sim/combat.rs
+++ b/src/sim/combat.rs
@@ -1,4 +1,168 @@
-use super::*;
+use std::{
+    collections::{HashMap, HashSet},
+    fmt::Display,
+};
+
+use super::prelude::*;
+
+#[derive(Debug)]
+pub struct KillData {
+    pub killed: CreatureId,
+    pub killer: Option<CreatureId>,
+}
+
+#[derive(Clone, Debug)]
+pub struct Attack {
+    pub to_hit_modifier: i8,
+    pub threat_treshold: i8,
+    pub armor_class: i8,
+}
+
+#[derive(Debug)]
+pub enum AttackResult {
+    CritMiss,
+    Miss,
+    Hit,
+    Crit,
+}
+
+#[derive(Clone, Debug)]
+pub struct AttackRoll {
+    pub attack: Attack,
+    pub roll: i8,
+    pub threat_roll: Option<i8>,
+}
+
+impl AttackRoll {
+    pub fn roll(attack: Attack, roll_fn: fn() -> i8) -> Self {
+        let roll = roll_fn();
+        let mut threat_roll = None;
+        if roll >= attack.threat_treshold {
+            threat_roll = Some(roll_fn());
+        }
+        Self {
+            attack,
+            roll,
+            threat_roll,
+        }
+    }
+
+    pub fn is_crit_miss(&self) -> bool {
+        self.roll == 1
+    }
+
+    pub fn is_auto_hit(&self) -> bool {
+        self.roll == 20
+    }
+
+    pub fn is_hit(&self) -> bool {
+        if self.is_crit_miss() {
+            return false;
+        }
+        if self.is_auto_hit() {
+            return true;
+        }
+        (self.roll + self.attack.to_hit_modifier) >= self.attack.armor_class
+    }
+
+    pub fn is_crit(&self) -> bool {
+        match self.threat_roll {
+            Some(roll) => (roll + self.attack.to_hit_modifier) >= self.attack.armor_class,
+            None => false,
+        }
+    }
+
+    pub fn result(&self) -> AttackResult {
+        if self.is_crit_miss() {
+            return AttackResult::CritMiss;
+        }
+        match self.is_hit() {
+            true => {
+                if self.is_crit() {
+                    AttackResult::Crit
+                } else {
+                    AttackResult::Hit
+                }
+            }
+            false => AttackResult::Miss,
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct AttackData {
+    pub target: CreatureId,
+    pub attacker: Option<CreatureId>,
+    pub attack_roll: AttackRoll,
+    pub damage: Option<i32>,
+    pub is_deathblow: bool,
+}
+
+impl Display for AttackData {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        if let Some(damage) = self.damage {
+            write!(f, "{damage} damage ")?;
+        }
+        match self.attack_roll.result() {
+            AttackResult::CritMiss => write!(f, "*Critical Miss* ")?,
+            AttackResult::Miss => write!(f, "*Miss* ")?,
+            AttackResult::Crit => write!(f, "!Critical hit! ")?,
+            _ => (),
+        };
+        let mod_symbol = if self.attack_roll.attack.to_hit_modifier >= 0 {
+            '+'
+        } else {
+            '-'
+        };
+        write!(
+            f,
+            ": {total} ({calc_roll} {calc_symbol} {calc_mod}) vs. {ac}",
+            total = self.attack_roll.roll + self.attack_roll.attack.to_hit_modifier,
+            calc_roll = self.attack_roll.roll,
+            calc_symbol = mod_symbol,
+            calc_mod = self.attack_roll.attack.to_hit_modifier.abs(),
+            ac = self.attack_roll.attack.armor_class,
+        )?;
+        write!(
+            f,
+            "{}",
+            if self.is_deathblow {
+                " - Killing blow!"
+            } else {
+                ""
+            }
+        )
+    }
+}
+
+#[derive(Debug)]
+pub struct CombatResults {
+    pub kills: Vec<KillData>,
+    pub attacks: Vec<AttackData>,
+}
+
+#[derive(Debug)]
+struct CombatState {
+    creature: Creature,
+    damage: i32,
+    enemies: HashSet<CreatureId>,
+}
+
+impl CombatState {
+    pub fn is_alive(&self) -> bool {
+        self.damage < self.creature.health()
+    }
+}
+
+impl CombatState {
+    pub fn from_creature(creature: Creature) -> Self {
+        Self {
+            creature,
+            damage: 0,
+            enemies: HashSet::new(),
+        }
+    }
+}
 
 pub fn resolve_combat(combatants: &[Creature], max_rounds: u16) -> Option<CombatResults> {
     let mut participants: HashMap<CreatureId, CombatState> = HashMap::new();
@@ -13,13 +177,21 @@ pub fn resolve_combat(combatants: &[Creature], max_rounds: u16) -> Option<Combat
             let is_enemy = c1.definition.id != c2.definition.id;
             if is_enemy {
                 participants
-                    .entry(c1.id)
+                    .entry(c1.id())
                     .or_insert(CombatState::from_creature(c1.clone()));
                 participants
-                    .entry(c2.id)
+                    .entry(c2.id())
                     .or_insert(CombatState::from_creature(c2.clone()));
-                participants.get_mut(&c1.id).unwrap().enemies.insert(c2.id);
-                participants.get_mut(&c2.id).unwrap().enemies.insert(c1.id);
+                participants
+                    .get_mut(&c1.id())
+                    .unwrap()
+                    .enemies
+                    .insert(c2.id());
+                participants
+                    .get_mut(&c2.id())
+                    .unwrap()
+                    .enemies
+                    .insert(c1.id());
             }
         }
     }
diff --git a/src/sim/creature.rs b/src/sim/creature.rs
new file mode 100644
index 0000000..29850a2
--- /dev/null
+++ b/src/sim/creature.rs
@@ -0,0 +1,76 @@
+use std::fmt::Display;
+
+use serde::{Deserialize, Serialize};
+use uuid::Uuid;
+
+use super::prelude::*;
+
+#[derive(Clone, Default, Eq, PartialEq, Hash, Debug, Serialize, Deserialize)]
+pub struct CreatureState {
+    pub damage: i32,
+}
+
+#[derive(Clone, Copy, Eq, PartialEq, Hash, Debug, Serialize, Deserialize)]
+pub struct CreatureId(Uuid);
+
+impl CreatureId {
+    pub fn generate() -> Self {
+        Self(Uuid::new_v4())
+    }
+}
+
+impl Display for CreatureId {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "c-{}", self.0)
+    }
+}
+
+#[derive(Clone, Eq, PartialEq, Hash, Debug, Serialize, Deserialize)]
+pub struct Creature {
+    id: CreatureId,
+    pub definition: CreatureDef,
+    pub state: CreatureState,
+}
+
+impl Creature {
+    pub fn generate_from_def(definition: CreatureDef) -> Self {
+        Self {
+            id: CreatureId::generate(),
+            state: CreatureState::default(),
+            definition,
+        }
+    }
+
+    pub fn id(&self) -> CreatureId {
+        self.id
+    }
+
+    pub fn patrol_chance(&self) -> f32 {
+        if self.definition.patrols {
+            0.5
+        } else {
+            0.0
+        }
+    }
+
+    pub fn health(&self) -> i32 {
+        self.definition.health - self.state.damage
+    }
+
+    pub fn is_alive(&self) -> bool {
+        self.health() > 0
+    }
+}
+
+impl Display for Creature {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "{singular} ({hp}/{max_hp}) [{id}]",
+            singular = self.definition.name_singular,
+            hp = self.health(),
+            max_hp = self.definition.health,
+            id = self.id
+        )
+    }
+}
diff --git a/src/sim/site.rs b/src/sim/site.rs
new file mode 100644
index 0000000..da7eb2d
--- /dev/null
+++ b/src/sim/site.rs
@@ -0,0 +1,255 @@
+use std::{collections::HashMap, fmt::Display, time::Duration};
+
+use serde::{Deserialize, Serialize};
+use uuid::Uuid;
+
+use super::prelude::*;
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash, Serialize, Deserialize)]
+pub struct SiteId(Uuid);
+
+impl SiteId {
+    pub fn generate() -> Self {
+        Self(Uuid::new_v4())
+    }
+}
+
+impl Display for SiteId {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "s-{}", self.0)
+    }
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct Site {
+    id: SiteId,
+    pub name: String,
+    pub definition: SiteDef,
+    areas: Vec<SiteArea>,
+    accumulated_time: Duration,
+}
+
+impl Site {
+    #[inline]
+    const fn minimum_tick() -> Duration {
+        Duration::from_secs(3600)
+    }
+
+    pub fn new(definition: SiteDef, name: impl Into<String>, areas: Vec<SiteArea>) -> Self {
+        Self {
+            id: SiteId::generate(),
+            definition,
+            name: name.into(),
+            areas,
+            accumulated_time: Duration::default(),
+        }
+    }
+
+    pub fn id(&self) -> SiteId {
+        self.id
+    }
+
+    fn inner_tick(&mut self) {
+        // Maps where creatures are going during patrol
+        let mut patrol_map: HashMap<CreatureId, (usize, usize)> = HashMap::new();
+        let site_size = self.areas.len();
+        for (area_index, area) in self.areas.iter_mut().enumerate() {
+            // Resolve combat per area
+            if let Some(results) = combat::resolve_combat(&area.population, 600) {
+                for attack in results.attacks {
+                    // println!(
+                    //     "{attacker} [{attacker_id}] attacks {target} [{target_id}]: {attack}",
+                    //     attacker = attack.attacker.map_or("Natural causes", |attacker| &area
+                    //         .find_creature(attacker)
+                    //         .unwrap()
+                    //         .definition
+                    //         .name_singular),
+                    //     attacker_id = attack
+                    //         .attacker
+                    //         .map_or("<no id>".into(), |id| id.to_string()),
+                    //     target = area
+                    //         .find_creature(attack.target)
+                    //         .unwrap()
+                    //         .definition
+                    //         .name_singular,
+                    //     target_id = attack.target
+                    // );
+                    if let Some(damage) = attack.damage {
+                        let target = match area
+                            .population
+                            .iter_mut()
+                            .find(|creature| creature.id() == attack.target)
+                        {
+                            Some(target) => target,
+                            None => continue,
+                        };
+                        target.state.damage = target.state.damage.saturating_add(damage);
+                    }
+                }
+                for death in results.kills {
+                    area.population
+                        .retain(|creature| creature.id() != death.killed);
+                }
+            }
+
+            // Resolve patrolling creatures
+            if site_size > 1 {
+                for creature in area.population.iter() {
+                    if fastrand::f32() < creature.patrol_chance() {
+                        // Make sure the creature patrols to a different area
+                        let target_index = {
+                            // Remove the current area from the range
+                            let index = fastrand::usize(0..site_size - 1);
+                            if index < area_index {
+                                index
+                            } else {
+                                // Skip the current area
+                                index + 1
+                            }
+                        };
+                        patrol_map.insert(creature.id(), (area_index, target_index));
+                    }
+                }
+            }
+        }
+
+        if !patrol_map.is_empty() {
+            println!("Patrols:");
+            for (id, (from, to)) in patrol_map.iter() {
+                println!("\t[{id}] patrols [{from}] -> [{to}]")
+            }
+        }
+
+        // Apply patrol map
+        for (creature_id, (from_index, to_index)) in patrol_map {
+            let creature = self
+                .areas
+                .get_mut(from_index)
+                .expect("Patrol: getting the area where the patrolling creature is")
+                .remove_creature(creature_id)
+                .expect("Patrol: finding the creature inside the area");
+            self.areas
+                .get_mut(to_index)
+                .expect("Patrol: getting the area where the creature is moving to")
+                .population
+                .push(creature);
+        }
+
+        println!("Tick! {}", self);
+    }
+
+    pub fn generate_from_def(site_def: &SiteDef) -> Self {
+        Self::new(
+            site_def.clone(),
+            "Gorbo's cave",
+            vec![
+                SiteArea::default();
+                fastrand::usize(site_def.min_size as usize..=site_def.max_size as usize)
+            ],
+        )
+    }
+
+    pub fn areas(&self) -> &Vec<SiteArea> {
+        self.areas.as_ref()
+    }
+
+    pub fn areas_mut(&mut self) -> &mut Vec<SiteArea> {
+        self.areas.as_mut()
+    }
+
+    pub fn populate_randomly(&mut self, creature_defs: &[&CreatureDef]) {
+        let area_count = self.areas.len();
+        {
+            let min_count = area_count;
+            let max_count = (5 + (area_count - 1) * 3).max(min_count);
+            for _ in 0..fastrand::usize(min_count..=max_count) {
+                let area_t = fastrand::f32().powi(2);
+                let index = (area_t * (area_count - 1) as f32).round() as usize;
+                let creature = Creature::generate_from_def(
+                    (*fastrand::choice(creature_defs.iter()).unwrap()).clone(),
+                );
+                self.areas
+                    .get_mut(index)
+                    .expect("Creature generation index for depth is out of bounds")
+                    .population
+                    .push(creature)
+            }
+        }
+    }
+
+    pub fn advance_time(&mut self, time: Duration) {
+        self.accumulated_time += time;
+        while self.accumulated_time >= Self::minimum_tick() {
+            self.inner_tick();
+            self.accumulated_time -= Self::minimum_tick();
+        }
+    }
+
+    /// Finds a creature with given id, removes it from the site and returns it with ownership
+    pub fn remove_creature(&mut self, id: CreatureId) -> Option<Creature> {
+        for area in self.areas.iter_mut() {
+            if let Some(creature) = area.remove_creature(id) {
+                return Some(creature);
+            }
+        }
+        None
+    }
+}
+
+impl Display for Site {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "site \"{name}\" [{id}] [",
+            name = self.name,
+            id = self.id
+        )?;
+        for (index, area) in self.areas.iter().enumerate() {
+            write!(f, "\n\tarea {} [", index)?;
+            for creature in area.population.iter() {
+                write!(f, "\n\t\t{}", creature)?;
+            }
+            if !area.population.is_empty() {
+                write!(f, "\n\t")?;
+            }
+            write!(f, "]")?;
+        }
+        if !self.areas.is_empty() {
+            writeln!(f)?;
+        }
+        write!(f, "]")
+    }
+}
+
+#[derive(Clone, Debug, Default, Serialize, Deserialize)]
+pub struct SiteArea {
+    pub population: Vec<Creature>,
+}
+
+impl SiteArea {
+    pub fn from_creatures(creatures: &[Creature]) -> Self {
+        Self {
+            population: creatures.to_vec(),
+        }
+    }
+
+    pub fn find_creature(&self, id: CreatureId) -> Option<&Creature> {
+        self.population.iter().find(|creature| creature.id() == id)
+    }
+
+    pub fn find_creature_mut(&mut self, id: CreatureId) -> Option<&mut Creature> {
+        self.population
+            .iter_mut()
+            .find(|creature| creature.id() == id)
+    }
+
+    /// Finds a creature with given id, removes it from the area and returns it with ownership
+    pub fn remove_creature(&mut self, id: CreatureId) -> Option<Creature> {
+        for i in 0..self.population.len() {
+            if self.population[i].id() == id {
+                return Some(self.population.swap_remove(i));
+            }
+        }
+        None
+    }
+}
diff --git a/src/sim/travel_group.rs b/src/sim/travel_group.rs
new file mode 100644
index 0000000..4e3926e
--- /dev/null
+++ b/src/sim/travel_group.rs
@@ -0,0 +1,26 @@
+use serde::{Deserialize, Serialize};
+
+use super::prelude::*;
+
+#[derive(Eq, PartialEq, Hash, Debug, Serialize, Deserialize)]
+pub struct TravelGroup {
+    pub creatures: Vec<Creature>,
+    pub position: WorldCoords,
+}
+
+impl TravelGroup {
+    pub fn new(creatures: Vec<Creature>, position: WorldCoords) -> Self {
+        Self {
+            creatures,
+            position,
+        }
+    }
+
+    pub fn insert(&mut self, creature: Creature) {
+        self.creatures.push(creature)
+    }
+
+    pub fn remove(&mut self, id: CreatureId) {
+        self.creatures.retain(|creature| creature.id() != id);
+    }
+}
diff --git a/src/sim/types.rs b/src/sim/util.rs
similarity index 77%
rename from src/sim/types.rs
rename to src/sim/util.rs
index ea502b9..4b4de2d 100644
--- a/src/sim/types.rs
+++ b/src/sim/util.rs
@@ -5,3 +5,7 @@ pub struct WorldCoords {
     pub x: i32,
     pub y: i32,
 }
+
+pub fn roll_d20() -> i8 {
+    fastrand::i8(1..=20)
+}
diff --git a/src/sim/world.rs b/src/sim/world.rs
new file mode 100644
index 0000000..4281c97
--- /dev/null
+++ b/src/sim/world.rs
@@ -0,0 +1,18 @@
+use std::time::Duration;
+
+use serde::{Deserialize, Serialize};
+
+use super::prelude::*;
+
+#[derive(Debug, Default, Serialize, Deserialize)]
+pub struct World {
+    pub sites: Vec<Site>,
+}
+
+impl World {
+    pub fn advance_time(&mut self, time: Duration) {
+        for site in self.sites.iter_mut() {
+            site.advance_time(time);
+        }
+    }
+}