diff --git a/Engine/src/live/AnimalEntity.ts b/Engine/src/live/AnimalEntity.ts
index 9b1debf..2d45683 100644
--- a/Engine/src/live/AnimalEntity.ts
+++ b/Engine/src/live/AnimalEntity.ts
@@ -1,6 +1,7 @@
 import * as planck from 'planck'
+import { AnimalDefinition, CreatureDefinition } from '../data/animals'
 import { Action } from "./Action"
-import { Entity } from "./Entity"
+import { Entity, Sensor } from "./Entity"
 import { PuddleEntity } from './PuddleEntity'
 import { WorldContext } from './World'
 
@@ -8,9 +9,19 @@ export class AnimalEntity extends Entity {
   action?: Action
   puddleTimer: number = 0
   isPlayer: boolean = false
+  isMonster: boolean = false
+  thinkTimer: number = 0 // Time since last thought, used by AI.
+  target?: Entity
+  def: AnimalDefinition
+  mode: CreatureDefinition
 
-  constructor(ctor: string) {
-    super(ctor)
+  constructor(def: AnimalDefinition) {
+    super(`${def.name}.animal.stand.west.0`)
+    this.def = def
+    this.mode = def.animal
+    this.maxSpeed = def.animal.maxSpeed
+    this.acceleration = def.animal.acceleration
+    this.turnRate = def.animal.turnRate
   }
   act(actions: Action[]) {
     this.action = actions.sort((a, b) => {
@@ -46,9 +57,9 @@ export class AnimalEntity extends Entity {
         case 'west':
           if (this.direction !== 0) {
             if (this.direction < 180) {
-              this.direction -= this.turnRate
+              this.direction -= this.mode.turnRate
             } else {
-              this.direction += this.turnRate
+              this.direction += this.mode.turnRate
             }
           }
           shouldMove = true
@@ -56,9 +67,9 @@ export class AnimalEntity extends Entity {
         case 'east':
           if (this.direction !== 180) {
             if (this.direction < 180) {
-              this.direction += this.turnRate
+              this.direction += this.mode.turnRate
             } else {
-              this.direction -= this.turnRate
+              this.direction -= this.mode.turnRate
             }
           }
           shouldMove = true
@@ -66,9 +77,9 @@ export class AnimalEntity extends Entity {
         case 'north':
           if (this.direction !== 90) {
             if (this.direction < 90 || this.direction > 270) {
-              this.direction += this.turnRate
+              this.direction += this.mode.turnRate
             } else {
-              this.direction -= this.turnRate
+              this.direction -= this.mode.turnRate
             }
           }
           shouldMove = true
@@ -76,9 +87,9 @@ export class AnimalEntity extends Entity {
         case 'south':
           if (this.direction !== 270) {
             if (this.direction > 90 && this.direction < 270) {
-              this.direction += this.turnRate
+              this.direction += this.mode.turnRate
             } else {
-              this.direction -= this.turnRate
+              this.direction -= this.mode.turnRate
             }
           }
           shouldMove = true
@@ -93,11 +104,11 @@ export class AnimalEntity extends Entity {
 
     if (shouldMove) {
       let r = this.direction * (Math.PI/180)
-      if (Math.abs(this.velocity[0]) < this.maxSpeed) {
-        this.velocity[0] -= Math.cos(r) * this.acceleration
+      if (Math.abs(this.velocity[0]) < this.mode.maxSpeed) {
+        this.velocity[0] -= Math.cos(r) * this.mode.acceleration
       }
-      if (Math.abs(this.velocity[1]) < this.maxSpeed) {
-        this.velocity[1] -= Math.sin(r) * this.acceleration
+      if (Math.abs(this.velocity[1]) < this.mode.maxSpeed) {
+        this.velocity[1] -= Math.sin(r) * this.mode.acceleration
       }
       let cardinal = this.getCardinal()
       this.sprite.setKey = 'run'
@@ -131,6 +142,73 @@ export class AnimalEntity extends Entity {
     }
     return 'south'
   }
+  think(delta: number) {
+    this.thinkTimer += delta
+    while (this.thinkTimer >= 500) {
+      if (!this.isMonster) {
+        if (this.target) {
+          // Flee from target
+        } else {
+          // Wander.
+        }
+      }
+      this.thinkTimer -= 500
+    }
+  }
+  setTarget(entity: Entity) {
+  }
+  sense(sensor: Sensor, entity: AnimalEntity) {
+    if (this.isPlayer) return
+    if (sensor.type === 'long') {
+      this.smell(entity)
+    } else {
+      this.see(entity)
+    }
+  }
+  lost(sensor: Sensor, entity: AnimalEntity) {
+    if (this.isPlayer) return
+    if (sensor.type === 'long') {
+      this.unsmell(entity)
+    } else {
+      this.unsee(entity)
+    }
+  }
+  smell(entity: AnimalEntity) {
+    if (entity.isPlayer) {
+      if (!this.isMonster) {
+        console.log('alert, we can smell player')
+      } else {
+        console.log('we smell the player, wander towards them')
+      }
+    }
+  }
+  unsmell(entity: AnimalEntity) {
+    if (entity.isPlayer) {
+      if (!this.isMonster) {
+        console.log('no longer smell player, wander around')
+      } else {
+        console.log('no longer smell player, wander around')
+      }
+    }
+  }
+  see(entity: AnimalEntity) {
+    if (entity.isPlayer) {
+      if (!this.isMonster) {
+        console.log('oh no, run from player')
+      } else {
+        console.log('oh ho, chase player')
+      }
+    }
+  }
+  unsee(entity: AnimalEntity) {
+    if (entity.isPlayer) {
+      if (!this.isMonster) {
+        console.log('oh ye, we safe')
+      } else {
+        console.log('hunt last seen location')
+      }
+    }
+  }
 }
 
 export function isAnimalEntity(o: any): o is AnimalEntity {
diff --git a/Engine/src/states/Game.ts b/Engine/src/states/Game.ts
index de6cdb3..d6c311b 100644
--- a/Engine/src/states/Game.ts
+++ b/Engine/src/states/Game.ts
@@ -9,10 +9,11 @@ import { SpriteInstance, sprites } from "../shared/sprites"
 import { ShapeCircle, ShapePoints } from "../data/sprite"
 import { SegmentZone } from "../data/segment"
 import { Zone } from "../live/Zone"
-import { Entity } from "../live/Entity"
+import { Entity, Sensor } from "../live/Entity"
 import { AnimalEntity, isAnimalEntity } from "../live/AnimalEntity"
 import { Action } from "../live/Action"
 import { WorldContext } from "../live/World"
+import { animals } from "../data/animals"
 
 export interface PIXIMissingColorMatrix extends PIXI.Filter {
   night(intensity: number, multiply: boolean): void
@@ -38,6 +39,7 @@ export function GameState(ctx: ContextI): StateI {
   let nightTime = 30 * 1000
   let dayTime = 30 * 1000
   let lastTime: number = performance.now()
+  let player: AnimalEntity
 
   let world: planck.World = planck.World({
     gravity: planck.Vec2(0, 0),
@@ -58,6 +60,16 @@ export function GameState(ctx: ContextI): StateI {
         b.addEntityContact(a)
       }
     }
+    if (a instanceof Sensor && a.entity instanceof AnimalEntity) {
+      if (b instanceof AnimalEntity) {
+        a.entity.sense(a, b)
+      }
+    }
+    if (b instanceof Sensor && b.entity instanceof AnimalEntity) {
+      if (a instanceof AnimalEntity) {
+        b.entity.sense(b, a)
+      }
+    }
   })
   world.on('end-contact', (contact: planck.Contact) => {
     let a = contact.getFixtureA().getUserData()
@@ -72,6 +84,16 @@ export function GameState(ctx: ContextI): StateI {
         b.removeEntityContact(a)
       }
     }
+    if (a instanceof Sensor && a.entity instanceof AnimalEntity) {
+      if (b instanceof AnimalEntity) {
+        a.entity.lost(a, b)
+      }
+    }
+    if (b instanceof Sensor && b.entity instanceof AnimalEntity) {
+      if (a instanceof AnimalEntity) {
+        b.entity.lost(b, a)
+      }
+    }
   })
 
   let rootContainer = new PIXI.Container()
@@ -145,14 +167,13 @@ export function GameState(ctx: ContextI): StateI {
       addZone(new Zone(z))
     }
 
-    // Add bogus entity
-    let player = new AnimalEntity('deer.animal.stand.west.0')
+    // Add player entity
+    player = new AnimalEntity(animals.deer)
     player.isPlayer = true
-
     addEntity(player, 'objects', 300, 100)
 
     // Add fake others
-    addEntity(new AnimalEntity('deer.animal.stand.west.0'), 'objects', 200, 200)
+    addEntity(new AnimalEntity(animals.turkey), 'objects', 200, 200)
 
     ctx.app.stage.addChild(rootContainer)
   }
@@ -190,11 +211,21 @@ export function GameState(ctx: ContextI): StateI {
       }
     }
     for (let entity of entities) {
-      if (isAnimalEntity(entity) && entity.isPlayer) {
-        entity.act(desiredActions)
-        // FIXME: This isn't the right place for this.
-        rootContainer.position.set(Math.round(ctx.app.renderer.width/2), Math.round(ctx.app.renderer.height/2))
-        rootContainer.pivot.set(Math.max(rootContainer.width/6, Math.min(entity.x, rootContainer.width/3)), Math.max(rootContainer.height/6, Math.min(entity.y, rootContainer.height/3)))
+      if (isAnimalEntity(entity)) {
+        if (entity.isPlayer) {
+          entity.act(desiredActions)
+          // FIXME: This isn't the right place for this.
+          rootContainer.position.set(Math.round(ctx.app.renderer.width/2), Math.round(ctx.app.renderer.height/2))
+          rootContainer.pivot.set(Math.max(rootContainer.width/6, Math.min(entity.x, rootContainer.width/3)), Math.max(rootContainer.height/6, Math.min(entity.y, rootContainer.height/3)))
+        } else {
+          //if (entity.body?.)
+          // Some sort of simple AI.
+          if (!entity.isMonster) {
+            // Slowly wander and run from player if close.
+          } else {
+            // Heavily wander and run towards player if close.
+          }
+        }
       } else {
         //console.log('hmm, we do be tickin', entity, entity.x, entity.y)
       }
@@ -237,6 +268,25 @@ export function GameState(ctx: ContextI): StateI {
         fixture.setUserData(entity)
         entity.body = body
         body.setUserData(entity)
+        // Sensors
+        let defaultShort = 50
+        let defaultLong = 100
+        if (entity instanceof AnimalEntity) {
+          defaultLong = entity.def.animal.scent
+          defaultShort = entity.def.animal.sight
+        }
+        // Create a short sensor (vision).
+        let senseFixture = body.createFixture({
+          shape: planck.Circle(planck.Vec2(entity.x, entity.y), defaultShort),
+          isSensor: true,
+        })
+        senseFixture.setUserData(new Sensor(entity, senseFixture, 'short'))
+        // Create a long sensor (scent).
+        let longSenseFixture = body.createFixture({
+          shape: planck.Circle(planck.Vec2(entity.x, entity.y), defaultLong),
+          isSensor: true,
+        })
+        longSenseFixture.setUserData(new Sensor(entity, longSenseFixture, 'long'))
       }
     }
     entity.x = x