diff --git a/src/main/java/gg/malloc/defense/GameEventHandler.java b/src/main/java/gg/malloc/defense/GameEventHandler.java
index 1b1a81a..a13bb1e 100644
--- a/src/main/java/gg/malloc/defense/GameEventHandler.java
+++ b/src/main/java/gg/malloc/defense/GameEventHandler.java
@@ -1,5 +1,7 @@
 package gg.malloc.defense;
 
+import gg.malloc.defense.engine.GameRunner;
+
 import org.bukkit.event.EventHandler;
 import org.bukkit.event.Listener;
 import org.bukkit.event.entity.EntityDeathEvent;
diff --git a/src/main/java/gg/malloc/defense/GameRunner.java b/src/main/java/gg/malloc/defense/GameRunner.java
deleted file mode 100644
index 9c4dbdd..0000000
--- a/src/main/java/gg/malloc/defense/GameRunner.java
+++ /dev/null
@@ -1,381 +0,0 @@
-package gg.malloc.defense;
-
-import gg.malloc.defense.model.Game;
-import gg.malloc.defense.model.Arena;
-import gg.malloc.defense.model.Spawnpoint;
-import gg.malloc.defense.model.Spawner;
-import gg.malloc.defense.model.Wave;
-
-import java.util.ArrayList;
-import java.util.HashSet;
-import java.util.logging.Logger;
-
-import org.bukkit.Bukkit;
-import org.bukkit.World;
-import org.bukkit.GameMode;
-import org.bukkit.attribute.Attribute;
-import org.bukkit.boss.BarColor;
-import org.bukkit.boss.BarStyle;
-import org.bukkit.boss.BossBar;
-import org.bukkit.event.player.PlayerTeleportEvent;
-import org.bukkit.event.entity.EntityDamageEvent;
-import org.bukkit.entity.Entity;
-import org.bukkit.entity.LivingEntity;
-import org.bukkit.entity.EntityType;
-import org.bukkit.entity.Player;
-import org.bukkit.scheduler.BukkitTask;
-
-public class GameRunner {
-  HashSet<Entity> m_livingMobs = new HashSet<>();
-  int m_createdMobs = 0;
-  int m_killedMobs = 0;
-  Arena m_arena;
-  Game m_game;
-  State m_state;
-  HashSet<Player> m_players = new HashSet<>();
-  HashSet<Player> m_livingPlayers = new HashSet<>();
-  Plugin m_plugin;
-
-  BossBar m_gameBar = Bukkit.createBossBar("Malloc Defense", BarColor.PURPLE, BarStyle.SOLID);
-  BossBar m_waveBar = Bukkit.createBossBar("Malloc Defense", BarColor.PURPLE, BarStyle.SOLID);
-  BukkitTask m_countdownTask;
-
-  int m_currentWaveNum = 0;
-  int m_currentBatch = 0;
-  Wave m_currentWave = null;
-
-  Logger m_log;
-
-  enum State {
-    Idle,
-    Warmup,
-    Playing,
-    GameOver
-  }
-
-  public GameRunner(Plugin plugin, Game game, Arena arena) {
-    m_plugin = plugin;
-    m_game = game;
-    m_arena = arena;
-    m_state = State.Idle;
-    m_gameBar.setVisible(true);
-    m_waveBar.setVisible(false);
-    m_log = m_plugin.getLogger();
-  }
-
-  int m_warmupCountdown = 0;
-
-  public void handleEntityDamage(EntityDamageEvent evt) {
-    Entity entity = evt.getEntity();
-    m_log.info("Damage " + entity);
-    m_log.info("Living Mobs " + m_livingMobs);
-    if (m_livingMobs.contains(entity)) {
-      m_game.onMobDamaged(entity);
-    }
-  }
-
-  private void countdownTick() {
-    if (m_warmupCountdown == 0) {
-      requestTransition(State.Playing);
-    } else {
-      updateMobBars();
-      broadcastMessage("Starting game in " + m_warmupCountdown);
-      m_warmupCountdown--;
-      m_countdownTask = m_plugin.getServer().getScheduler().runTaskLater(m_plugin, () -> {
-        countdownTick();
-      }, 20);
-    }
-  }
-
-  private void clearMobs() {
-    for(Entity e : m_livingMobs) {
-      e.remove();
-    }
-    m_livingMobs.clear();
-    m_createdMobs = 0;
-    m_killedMobs = 0;
-  }
-
-  private boolean enterIdle() {
-    broadcastMessage("Game state: Idle");
-    m_currentWaveNum = 0;
-    m_livingPlayers.clear();
-    for(Player p : m_players) {
-      m_livingPlayers.add(p);
-    }
-    if (m_countdownTask != null) {
-      m_countdownTask.cancel();
-      m_countdownTask = null;
-    }
-    clearMobs();
-    return true;
-  }
-
-  private boolean enterWarmup() {
-    m_log.info("Game state: Warmup");
-    m_currentWaveNum += 1;
-    m_currentWave = m_game.getWave(m_currentWaveNum);
-    m_warmupCountdown = 10;
-    for(Player p : m_players) {
-      m_livingPlayers.add(p);
-    }
-    broadcastTitle("Warmup", "Prepare yourself for wave " + m_currentWaveNum);
-    clearMobs();
-    countdownTick();
-    return true;
-  }
-
-  private boolean enterPlaying() {
-    m_log.info("Game state: Playing");
-    m_log.info("Starting wave " + m_currentWaveNum);
-    m_currentBatch = 1;
-    spawnNextBatch();
-    broadcastTitle("Wave " + m_currentWaveNum);
-    return true;
-  }
-
-  private boolean enterGameOver() {
-    broadcastTitle("Game Over!");
-    if (m_countdownTask != null) {
-      m_countdownTask.cancel();
-      m_countdownTask = null;
-    }
-    clearMobs();
-    for(Player p : m_players) {
-      removePlayer(p);
-    }
-    return true;
-  }
-
-  private void updateMobBars() {
-    m_gameBar.setVisible(true);
-    switch(m_state) {
-      case Idle:
-        m_gameBar.setProgress(1.0);
-        m_gameBar.setTitle("Waiting for playres...");
-        m_gameBar.setColor(BarColor.PURPLE);
-        m_waveBar.setVisible(false);
-        break;
-      case Warmup:
-        m_gameBar.setProgress((double)m_currentWaveNum / (double)m_game.getWaveCount());
-        m_gameBar.setTitle("Wave " + m_currentWaveNum + " / " + m_game.getWaveCount());
-        m_gameBar.setColor(BarColor.PURPLE);
-        m_waveBar.setVisible(true);
-        m_waveBar.setColor(BarColor.YELLOW);
-        m_waveBar.setTitle("Warmup");
-        m_waveBar.setProgress((double)m_warmupCountdown / (double)10);
-        break;
-      case Playing:
-        m_gameBar.setProgress((double)m_currentWaveNum / (double)m_game.getWaveCount());
-        m_gameBar.setTitle("Wave " + m_currentWaveNum + " / " + m_game.getWaveCount());
-        m_gameBar.setColor(BarColor.PURPLE);
-        if (m_createdMobs > 0) {
-          m_waveBar.setVisible(true);
-          m_waveBar.setColor(BarColor.GREEN);
-          m_waveBar.setTitle("Mobs remaining: " + (m_createdMobs - m_killedMobs));
-          m_waveBar.setProgress((double)m_killedMobs / (double)m_createdMobs);
-        } else {
-          m_waveBar.setVisible(false);
-        }
-        break;
-      case GameOver:
-        m_gameBar.setColor(BarColor.RED);
-        m_gameBar.setProgress(1.0);
-        m_gameBar.setTitle("Game Over!");
-        m_waveBar.setVisible(false);
-        break;
-    }
-  }
-
-  private void spawnNextBatch() {
-    broadcastMessage("Spawning batch " + m_currentBatch);
-    Spawner spawner = new GameSpawner(m_arena.spawnpoints());
-    m_currentWave.spawnBatch(spawner, m_currentBatch);
-    updateMobBars();
-  }
-
-  public void handlePlayerDeath(Player player) {
-    if (m_livingPlayers.contains(player)) {
-      m_log.info("Player has died in game" + player);
-      m_livingPlayers.remove(player);
-      m_arena.getWorld().strikeLightningEffect(player.getLocation());
-      player.setGameMode(GameMode.SPECTATOR);
-      if (m_livingPlayers.size() == 0) {
-        broadcastMessage("Everyone is dead :(");
-        requestTransition(State.GameOver);
-      } else {
-        m_log.info("Remaining players " + m_livingPlayers.size());
-      }
-    }
-  }
-
-  public void handleEntityDeath(Entity entity) {
-    if (m_livingMobs.contains(entity)) {
-      broadcastMessage("Killed game entity " + entity);
-      m_livingMobs.remove(entity);
-      m_killedMobs += 1;
-      updateMobBars();
-      if (m_livingMobs.size() <= 3) {
-        m_log.info("Starting next batch!");
-        if (m_currentBatch >= m_currentWave.batchCount()) {
-          if (m_currentWaveNum >= m_game.getWaveCount()) {
-            requestTransition(State.GameOver);
-          } else if (m_livingMobs.size() == 0) {
-            requestTransition(State.Warmup);
-          }
-        } else {
-          m_currentBatch += 1;
-          spawnNextBatch();
-        }
-      } else {
-        m_log.fine("Living mobs remaining: " + m_livingMobs.size());
-      }
-    }
-  }
-
-  private boolean syncPlayer(Player player) {
-    m_log.fine("Synchronizing player " + player);
-    World playerWorld = player.getLocation().getWorld();
-    World gameWorld = m_arena.getWorld();
-    m_gameBar.addPlayer(player);
-    m_waveBar.addPlayer(player);
-    if (m_livingPlayers.contains(player)) {
-      m_log.fine("Player is alive, turning into adventure mode " + player);
-      if (player.getGameMode() != Bukkit.getDefaultGameMode()) {
-        player.setGameMode(Bukkit.getDefaultGameMode());
-        player.teleport(gameWorld.getSpawnLocation(), PlayerTeleportEvent.TeleportCause.PLUGIN);
-      }
-      player.setHealth(player.getAttribute(Attribute.GENERIC_MAX_HEALTH).getValue());
-      player.setFoodLevel(10);
-    } else {
-      m_log.fine("Player is dead, turning into spectator " + player);
-      player.setGameMode(GameMode.SPECTATOR);
-    }
-    if (playerWorld != gameWorld) {
-      m_log.info("Teleporting player " + player);
-      return player.teleport(gameWorld.getSpawnLocation(), PlayerTeleportEvent.TeleportCause.PLUGIN);
-    } else {
-      return false;
-    }
-  }
-
-  private boolean attemptTransition(State state) {
-    if (m_state == state) {
-      return false;
-    }
-    switch(state) {
-      case Idle:
-        return enterIdle();
-      case Warmup:
-        return enterWarmup();
-      case Playing:
-        return enterPlaying();
-      case GameOver:
-        return enterGameOver();
-    }
-    return false;
-  }
-  
-  private boolean validateTransition(State from, State to) {
-    switch(from) {
-      case Idle:
-        return to == State.Warmup;
-      case Warmup:
-        return to == State.Playing || to == State.Idle || to == State.GameOver;
-      case Playing:
-        return to == State.Warmup || to == State.GameOver || to == State.Idle;
-      case GameOver:
-        return to == State.Idle;
-    }
-    return false;
-  }
-
-  public boolean requestTransition(State state) {
-    if (!validateTransition(m_state, state)) {
-      m_log.warning("Attemped illegal transition: " + m_state + " -> " + state);
-      return false;
-    }
-    if (attemptTransition(state)) {
-      updateMobBars();
-      m_log.info("Game transition: " + m_state + " -> " + state);
-      m_state = state;
-      for(Player p : m_players) {
-        syncPlayer(p);
-      }
-      return true;
-    }
-    m_log.severe("Failed to complete transition: " + m_state + " -> " + state);
-    return false;
-  }
-
-  public boolean addPlayer(Player p) {
-    if (m_state == State.Idle || m_state == State.Warmup) {
-      m_log.info("Adding player " + p);
-      m_players.add(p);
-      broadcastMessage(p.getName() + " has joined the game");
-      syncPlayer(p);
-      if (m_state == State.Idle) {
-        requestTransition(State.Warmup);
-      }
-      return true;
-    } else {
-      return false;
-    }
-  }
-
-  public void removePlayer(Player p) {
-    m_log.info("Removing player " + p); 
-    m_gameBar.removePlayer(p);
-    m_waveBar.removePlayer(p);
-    m_players.remove(p);
-    m_livingPlayers.remove(p);
-    p.setGameMode(Bukkit.getDefaultGameMode());
-    if (m_players.size() == 0) {
-      requestTransition(State.Idle);
-    }
-  }
-
-  void broadcastTitle(String title) {
-    broadcastTitle(title, "");
-  }
-
-  void broadcastTitle(String title, String subtitle) {
-    for(Player p : m_players) {
-      p.sendTitle(title, subtitle, 10, 70, 20);
-    }
-  }
-
-  void broadcastMessage(String string) {
-    World world = m_arena.getWorld();
-    for(Player p : world.getPlayers()) {
-      p.sendMessage(string);
-    }
-  }
-
-  void registerSpawnedMob(Entity entity) {
-    m_log.fine("Registered new mob " + entity); 
-    m_livingMobs.add(entity);
-    m_createdMobs += 1;
-  }
-
-  private class GameSpawner implements Spawner {
-    Spawnpoint[] m_spawnpoints;
-    int m_spawnIdx = 0;
- 
-    public GameSpawner(Spawnpoint[] spawnpoints) {
-      m_spawnpoints = spawnpoints;
-    }
-
-    @Override
-    public Entity spawnMob(EntityType type) {
-      m_log.fine("Spawning " + type + " at " + m_spawnpoints[m_spawnIdx]);
-      Entity newMob = m_arena.getWorld().spawnEntity(m_spawnpoints[m_spawnIdx].getLocation(), type);
-      LivingEntity livingMob = (LivingEntity)newMob;
-      livingMob.setRemoveWhenFarAway(false);
-      registerSpawnedMob(newMob);
-      m_spawnIdx += 1;
-      m_spawnIdx %= m_spawnpoints.length;
-      return newMob;
-    }
-  }
-}
diff --git a/src/main/java/gg/malloc/defense/Plugin.java b/src/main/java/gg/malloc/defense/Plugin.java
index e77f77d..ea07361 100644
--- a/src/main/java/gg/malloc/defense/Plugin.java
+++ b/src/main/java/gg/malloc/defense/Plugin.java
@@ -20,6 +20,11 @@ import gg.malloc.defense.model.Game;
 import gg.malloc.defense.games.LinearGame;
 import gg.malloc.defense.games.ScaledWaves;
 
+import gg.malloc.defense.engine.GameRunner;
+
+import gg.malloc.defense.commands.AddPlayerCommand;
+import gg.malloc.defense.commands.SetStageCommand;
+
 public class Plugin extends JavaPlugin {
   ArrayList<Arena> m_arenas = new ArrayList<>();
   ArrayList<Game> m_games = new ArrayList<>();
@@ -58,7 +63,7 @@ public class Plugin extends JavaPlugin {
     getLogger().setLevel(Level.FINEST);
     setupDemoGame();
     getCommand("setstage").setExecutor(new SetStageCommand(this));
-    getCommand("initgame").setExecutor(new InitGameCommand(this));
+    getCommand("addplayer").setExecutor(new AddPlayerCommand(this));
     getCommand("debuginfo").setExecutor(new DebuginfoCommand(this));
   }
 
diff --git a/src/main/java/gg/malloc/defense/InitGameCommand.java b/src/main/java/gg/malloc/defense/commands/AddPlayerCommand.java
similarity index 63%
rename from src/main/java/gg/malloc/defense/InitGameCommand.java
rename to src/main/java/gg/malloc/defense/commands/AddPlayerCommand.java
index 14c549b..7c97669 100644
--- a/src/main/java/gg/malloc/defense/InitGameCommand.java
+++ b/src/main/java/gg/malloc/defense/commands/AddPlayerCommand.java
@@ -1,14 +1,18 @@
-package gg.malloc.defense;
+package gg.malloc.defense.commands;
 
 import org.bukkit.command.Command;
 import org.bukkit.command.CommandExecutor;
 import org.bukkit.command.CommandSender;
 import org.bukkit.entity.Player;
 
-public class InitGameCommand implements CommandExecutor {
+import gg.malloc.defense.engine.GameRunner;
+
+import gg.malloc.defense.Plugin;
+
+public class AddPlayerCommand implements CommandExecutor {
   Plugin m_plugin;
 
-  public InitGameCommand(Plugin plugin) {
+  public AddPlayerCommand(Plugin plugin) {
     m_plugin = plugin;
   }
 
@@ -16,7 +20,7 @@ public class InitGameCommand implements CommandExecutor {
   public boolean onCommand(CommandSender sender, Command command, String s, String[] args) {
     String worldName = args[0];
     GameRunner runner = m_plugin.getRunnerForWorld(m_plugin.getServer().getWorld(worldName));
-    Player player= m_plugin.getServer().getPlayer(args[1]);
+    Player player = m_plugin.getServer().getPlayer(args[1]);
     runner.addPlayer(player);
     return true;
   }
diff --git a/src/main/java/gg/malloc/defense/SetStageCommand.java b/src/main/java/gg/malloc/defense/commands/SetStageCommand.java
similarity index 72%
rename from src/main/java/gg/malloc/defense/SetStageCommand.java
rename to src/main/java/gg/malloc/defense/commands/SetStageCommand.java
index 2fa1aa9..8d2997b 100644
--- a/src/main/java/gg/malloc/defense/SetStageCommand.java
+++ b/src/main/java/gg/malloc/defense/commands/SetStageCommand.java
@@ -1,10 +1,14 @@
-package gg.malloc.defense;
+package gg.malloc.defense.commands;
 
 import org.bukkit.command.Command;
 import org.bukkit.command.CommandExecutor;
 import org.bukkit.command.CommandSender;
 import org.bukkit.World;
 
+import gg.malloc.defense.engine.GameRunner;
+
+import gg.malloc.defense.Plugin;
+
 public class SetStageCommand implements CommandExecutor {
   Plugin m_plugin;
 
@@ -19,13 +23,13 @@ public class SetStageCommand implements CommandExecutor {
     String stateName = args[0].toLowerCase();
     boolean ret = false;
     if (stateName.equals("idle")) {
-      ret = runner.requestTransition(GameRunner.State.Idle);
+      ret = runner.requestTransition(GameRunner.Stage.Idle);
     } else if (stateName.equals("warmup")) {
-      ret = runner.requestTransition(GameRunner.State.Warmup);
+      ret = runner.requestTransition(GameRunner.Stage.Warmup);
     } else if (stateName.equals("playing")) {
-      ret = runner.requestTransition(GameRunner.State.Playing);
+      ret = runner.requestTransition(GameRunner.Stage.Playing);
     } else if (stateName.equals("gameover")) {
-      ret = runner.requestTransition(GameRunner.State.GameOver);
+      ret = runner.requestTransition(GameRunner.Stage.GameOver);
     } else {
       sender.sendMessage("Unknown state " + stateName);
       return false;
diff --git a/src/main/java/gg/malloc/defense/engine/GameRunner.java b/src/main/java/gg/malloc/defense/engine/GameRunner.java
new file mode 100644
index 0000000..4e212f7
--- /dev/null
+++ b/src/main/java/gg/malloc/defense/engine/GameRunner.java
@@ -0,0 +1,350 @@
+package gg.malloc.defense.engine;
+
+import gg.malloc.defense.model.Game;
+import gg.malloc.defense.model.Arena;
+import gg.malloc.defense.model.Spawner;
+import gg.malloc.defense.model.Wave;
+
+import gg.malloc.defense.Plugin;
+
+import java.util.logging.Logger;
+
+import org.bukkit.Bukkit;
+import org.bukkit.World;
+import org.bukkit.boss.BarColor;
+import org.bukkit.boss.BarStyle;
+import org.bukkit.boss.BossBar;
+import org.bukkit.event.player.PlayerTeleportEvent;
+import org.bukkit.event.entity.EntityDamageEvent;
+import org.bukkit.entity.Entity;
+import org.bukkit.entity.LivingEntity;
+import org.bukkit.entity.EntityType;
+import org.bukkit.entity.Player;
+import org.bukkit.scheduler.BukkitTask;
+
+public class GameRunner {
+  Arena m_arena;
+  Game m_game;
+  Stage m_stage;
+  Plugin m_plugin;
+
+  BossBar m_gameBar = Bukkit.createBossBar("Malloc Defense", BarColor.PURPLE, BarStyle.SOLID);
+  BossBar m_waveBar = Bukkit.createBossBar("Malloc Defense", BarColor.PURPLE, BarStyle.SOLID);
+  BukkitTask m_countdownTask;
+
+  MobManager m_mobs;
+  WaveManager m_waves;
+  PlayerManager m_players;
+
+  Logger m_log;
+
+  public enum Stage {
+    Idle,
+    Warmup,
+    Playing,
+    GameOver
+  }
+
+  class WaveManager {
+    int m_currentWaveNum = 0;
+    int m_currentBatch = 0;
+    Wave m_currentWave = null;
+    Game m_game;
+
+    WaveManager(Game game) {
+      m_game = game;
+    }
+
+    void reset() {
+      m_currentWaveNum = 0;
+      m_currentBatch = 0;
+      m_currentWave = null;
+    }
+
+    Wave currentWave() {
+      return m_currentWave;
+    }
+
+    int currentWaveNum() {
+      return m_currentWaveNum;
+    }
+
+    int currentBatchNum() {
+      return m_currentBatch;
+    }
+
+    double progress() {
+      return (double)m_currentWaveNum / (double)m_game.getWaveCount();
+    }
+
+    boolean isLastWave() {
+      return m_currentWaveNum >= m_game.getWaveCount();
+    }
+
+    boolean isLastBatch() {
+      return m_currentBatch >= m_currentWave.batchCount();
+    }
+
+    void nextBatch() {
+      m_currentBatch += 1;
+    }
+
+    void next() {
+      m_currentWaveNum += 1;
+      m_currentBatch = 0;
+      m_currentWave = m_game.getWave(m_currentWaveNum);
+    }
+  }
+
+
+  public GameRunner(Plugin plugin, Game game, Arena arena) {
+    m_plugin = plugin;
+    m_game = game;
+    m_arena = arena;
+    m_stage = Stage.Idle;
+    m_gameBar.setVisible(true);
+    m_waveBar.setVisible(false);
+    m_mobs = new MobManager(m_game);
+    m_waves = new WaveManager(m_game);
+    m_players = new PlayerManager();
+    m_log = m_plugin.getLogger();
+  }
+
+  int m_warmupCountdown = 0;
+
+  public void handleEntityDamage(EntityDamageEvent evt) {
+    m_mobs.handleEntityDamage(evt);
+  }
+
+  private void countdownTick() {
+    if (m_warmupCountdown == 0) {
+      requestTransition(Stage.Playing);
+    } else {
+      updateMobBars();
+      broadcastMessage("Starting game in " + m_warmupCountdown);
+      m_warmupCountdown--;
+      m_countdownTask = m_plugin.getServer().getScheduler().runTaskLater(m_plugin, () -> {
+        countdownTick();
+      }, 20);
+    }
+  }
+
+  private boolean enterIdle() {
+    m_waves.reset();
+    m_mobs.clear();
+    m_players.requestTransitionForAll(PlayerManager.State.Idle);
+    if (m_countdownTask != null) {
+      m_countdownTask.cancel();
+      m_countdownTask = null;
+    }
+    return true;
+  }
+
+  private boolean enterWarmup() {
+    m_waves.next();
+    m_warmupCountdown = 10;
+    for(Player p : m_players.getPlayers()) {
+        if (m_players.requestTransition(p, PlayerManager.State.Playing)) {
+          p.teleport(m_arena.getWorld().getSpawnLocation(), PlayerTeleportEvent.TeleportCause.PLUGIN);
+        }
+    }
+    broadcastTitle("Warmup", "Prepare yourself for wave " + m_waves.currentWaveNum());
+    m_mobs.clear();
+    countdownTick();
+    return true;
+  }
+
+  private boolean enterPlaying() {
+    m_log.info("Starting wave " + m_waves.currentWaveNum());
+    spawnNextBatch();
+    broadcastTitle("Wave " + m_waves.currentWaveNum());
+    return true;
+  }
+
+  private boolean enterGameOver() {
+    broadcastTitle("Game Over!");
+    if (m_countdownTask != null) {
+      m_countdownTask.cancel();
+      m_countdownTask = null;
+    }
+    m_mobs.clear();
+    for(Player p : m_players.getPlayers()) {
+      removePlayer(p);
+    }
+    return true;
+  }
+
+  private void updateMobBars() {
+    m_gameBar.setVisible(true);
+    switch(m_stage) {
+      case Idle:
+        m_gameBar.setProgress(1.0);
+        m_gameBar.setTitle("Waiting for playres...");
+        m_gameBar.setColor(BarColor.PURPLE);
+        m_waveBar.setVisible(false);
+        break;
+      case Warmup:
+        m_gameBar.setProgress(m_waves.progress());
+        m_gameBar.setTitle("Wave " + m_waves.currentWaveNum() + " / " + m_game.getWaveCount());
+        m_gameBar.setColor(BarColor.PURPLE);
+        m_waveBar.setVisible(true);
+        m_waveBar.setColor(BarColor.YELLOW);
+        m_waveBar.setTitle("Warmup");
+        m_waveBar.setProgress((double)m_warmupCountdown / (double)10);
+        break;
+      case Playing:
+        m_gameBar.setProgress(m_waves.progress());
+        m_gameBar.setTitle("Wave " + m_waves.currentWaveNum() + " / " + m_game.getWaveCount());
+        m_gameBar.setColor(BarColor.PURPLE);
+        if (m_mobs.createdMobs() > 0) {
+          m_waveBar.setVisible(true);
+          m_waveBar.setColor(BarColor.GREEN);
+          m_waveBar.setTitle("Mobs remaining: " + m_mobs.remainingMobs());
+          m_waveBar.setProgress(m_mobs.progress());
+        } else {
+          m_waveBar.setVisible(false);
+        }
+        break;
+      case GameOver:
+        m_gameBar.setColor(BarColor.RED);
+        m_gameBar.setProgress(1.0);
+        m_gameBar.setTitle("Game Over!");
+        m_waveBar.setVisible(false);
+        break;
+    }
+  }
+
+  private void spawnNextBatch() {
+    broadcastMessage("Spawning batch " + m_waves.currentBatchNum());
+    Spawner spawner = new GameSpawner(m_arena, m_mobs);
+    m_waves.currentWave().spawnBatch(spawner, m_waves.currentBatchNum());
+    updateMobBars();
+  }
+
+  public void handlePlayerDeath(Player player) {
+    if (m_players.requestTransition(player, PlayerManager.State.Dead)) {
+      m_arena.getWorld().strikeLightningEffect(player.getLocation());
+      if (!m_players.isAnyoneAlive()) {
+        broadcastMessage("Everyone is dead :(");
+        requestTransition(Stage.GameOver);
+      } else {
+        m_log.info("Remaining players " + m_players.remainingPlayers());
+      }
+    }
+  }
+
+  public void handleEntityDeath(Entity entity) {
+    if (m_mobs.killMob(entity)) {
+      broadcastMessage("Killed game entity " + entity);
+      updateMobBars();
+      if (m_mobs.remainingMobs() <= 3) {
+        m_log.info("Starting next batch!");
+        if (m_waves.isLastBatch()) {
+          if (m_waves.isLastWave()) {
+            requestTransition(Stage.GameOver);
+          } else if (m_mobs.empty()) {
+            requestTransition(Stage.Warmup);
+          }
+        } else {
+          m_waves.nextBatch();
+          spawnNextBatch();
+        }
+      } else {
+        m_log.fine("Living mobs remaining: " + m_mobs.remainingMobs());
+      }
+    }
+  }
+
+  private boolean attemptTransition(Stage stage) {
+    if (m_stage == stage) {
+      return false;
+    }
+    m_log.info("Game state: " + stage);
+    switch(stage) {
+      case Idle:
+        return enterIdle();
+      case Warmup:
+        return enterWarmup();
+      case Playing:
+        return enterPlaying();
+      case GameOver:
+        return enterGameOver();
+    }
+    return false;
+  }
+  
+  private boolean validateTransition(Stage from, Stage to) {
+    switch(from) {
+      case Idle:
+        return to == Stage.Warmup;
+      case Warmup:
+        return to == Stage.Playing || to == Stage.Idle || to == Stage.GameOver;
+      case Playing:
+        return to == Stage.Warmup || to == Stage.GameOver || to == Stage.Idle;
+      case GameOver:
+        return to == Stage.Idle;
+    }
+    return false;
+  }
+
+  public boolean requestTransition(Stage stage) {
+    if (!validateTransition(m_stage, stage)) {
+      m_log.warning("Attemped illegal transition: " + m_stage + " -> " + stage);
+      return false;
+    }
+    if (attemptTransition(stage)) {
+      m_log.info("Game transition: " + m_stage + " -> " + stage);
+      m_stage = stage;
+      updateMobBars();
+      return true;
+    }
+    m_log.severe("Failed to complete transition: " + m_stage + " -> " + stage);
+    return false;
+  }
+
+  public void addPlayer(Player p) {
+    m_players.addPlayer(p);
+    m_gameBar.addPlayer(p);
+    m_waveBar.addPlayer(p);
+    if (m_stage == Stage.Idle || m_stage == Stage.Warmup) {
+      if (m_players.requestTransition(p, PlayerManager.State.Playing)) {
+        p.teleport(m_arena.getWorld().getSpawnLocation(), PlayerTeleportEvent.TeleportCause.PLUGIN);
+      }
+      broadcastMessage(p.getName() + " has joined the game");
+      if (m_stage == Stage.Idle) {
+        requestTransition(Stage.Warmup);
+      }
+    }
+  }
+
+  public void removePlayer(Player p) {
+    m_gameBar.removePlayer(p);
+    m_waveBar.removePlayer(p);
+    m_players.removePlayer(p);
+    if (m_players.isEmpty()) {
+      requestTransition(Stage.Idle);
+    }
+  }
+
+  void broadcastTitle(String title) {
+    broadcastTitle(title, "");
+  }
+
+  void broadcastTitle(String title, String subtitle) {
+    for(Player p : m_players.getPlayers()) {
+      p.sendTitle(title, subtitle, 10, 70, 20);
+    }
+  }
+
+  void broadcastMessage(String string) {
+    World world = m_arena.getWorld();
+    for(Player p : world.getPlayers()) {
+      p.sendMessage(string);
+    }
+  }
+
+  void registerSpawnedMob(Entity entity) {
+    m_mobs.addEntity(entity);
+  }
+
+}
diff --git a/src/main/java/gg/malloc/defense/engine/GameSpawner.java b/src/main/java/gg/malloc/defense/engine/GameSpawner.java
new file mode 100644
index 0000000..2a5985b
--- /dev/null
+++ b/src/main/java/gg/malloc/defense/engine/GameSpawner.java
@@ -0,0 +1,33 @@
+package gg.malloc.defense.engine;
+
+import gg.malloc.defense.model.Spawner;
+import gg.malloc.defense.model.Spawnpoint;
+import gg.malloc.defense.model.Arena;
+
+import org.bukkit.entity.Entity;
+import org.bukkit.entity.LivingEntity;
+import org.bukkit.entity.EntityType;
+
+public class GameSpawner implements Spawner {
+  Arena m_arena;
+  MobManager m_manager;
+  int m_spawnIdx = 0;
+
+  public GameSpawner(Arena arena, MobManager manager) {
+    m_arena = arena;
+    m_manager = manager;
+  }
+
+  @Override
+  public Entity spawnMob(EntityType type) {
+    Spawnpoint[] spawnpoints = m_arena.spawnpoints();
+    m_spawnIdx %= spawnpoints.length;
+    //m_log.fine("Spawning " + type + " at " + spawnpoints[m_spawnIdx]);
+    Entity newMob = m_arena.getWorld().spawnEntity(spawnpoints[m_spawnIdx].getLocation(), type);
+    LivingEntity livingMob = (LivingEntity)newMob;
+    livingMob.setRemoveWhenFarAway(false);
+    m_manager.addEntity(newMob);
+    m_spawnIdx += 1;
+    return newMob;
+  }
+}
diff --git a/src/main/java/gg/malloc/defense/engine/GameStage.java b/src/main/java/gg/malloc/defense/engine/GameStage.java
new file mode 100644
index 0000000..63c8617
--- /dev/null
+++ b/src/main/java/gg/malloc/defense/engine/GameStage.java
@@ -0,0 +1,7 @@
+package gg.malloc.defense.engine;
+
+public interface GameStage {
+  String name();
+  default void onEnter() {}
+  default void onExit() {}
+}
diff --git a/src/main/java/gg/malloc/defense/engine/MobManager.java b/src/main/java/gg/malloc/defense/engine/MobManager.java
new file mode 100644
index 0000000..a7ab9ff
--- /dev/null
+++ b/src/main/java/gg/malloc/defense/engine/MobManager.java
@@ -0,0 +1,72 @@
+package gg.malloc.defense.engine;
+
+import java.util.HashSet;
+
+import org.bukkit.entity.Entity;
+import org.bukkit.event.entity.EntityDamageEvent;
+
+import gg.malloc.defense.model.Game;
+
+public class MobManager {
+  HashSet<Entity> m_livingMobs = new HashSet<>();
+  int m_createdMobs = 0;
+  int m_killedMobs = 0;
+
+  Game m_game;
+
+  MobManager(Game game) {
+    m_game = game;
+  }
+
+  public void handleEntityDamage(EntityDamageEvent evt) {
+    Entity entity = evt.getEntity();
+    //m_log.info("Damage " + entity);
+    //m_log.info("Living Mobs " + m_livingMobs);
+    if (m_livingMobs.contains(entity)) {
+      m_game.onMobDamaged(entity);
+    }
+  }
+
+  public boolean killMob(Entity entity) {
+    if (m_livingMobs.contains(entity)) {
+      m_killedMobs += 1;
+      return m_livingMobs.remove(entity);
+    }
+    return false;
+  }
+
+  public void clear() {
+    for(Entity e : m_livingMobs) {
+      e.remove();
+    }
+    m_livingMobs.clear();
+    m_createdMobs = 0;
+    m_killedMobs = 0;
+  }
+
+  public int createdMobs() {
+    return m_createdMobs;
+  }
+
+  public int killedMobs() {
+    return m_killedMobs;
+  }
+
+  public int remainingMobs() {
+    return m_createdMobs - m_killedMobs;
+  }
+
+  public double progress() {
+    return (double)m_killedMobs / (double)m_createdMobs;
+  }
+
+  public void addEntity(Entity entity) {
+    //m_log.fine("Registered new mob " + entity); 
+    m_livingMobs.add(entity);
+    m_createdMobs += 1;
+  }
+
+  public boolean empty() {
+    return m_livingMobs.size() == 0;
+  }
+}
diff --git a/src/main/java/gg/malloc/defense/engine/PlayerManager.java b/src/main/java/gg/malloc/defense/engine/PlayerManager.java
new file mode 100644
index 0000000..1c1bf39
--- /dev/null
+++ b/src/main/java/gg/malloc/defense/engine/PlayerManager.java
@@ -0,0 +1,113 @@
+package gg.malloc.defense.engine;
+
+import org.bukkit.entity.Player;
+import org.bukkit.Bukkit;
+import org.bukkit.GameMode;
+import org.bukkit.attribute.Attribute;
+import org.bukkit.event.player.PlayerTeleportEvent;
+
+import java.util.HashMap;
+import java.util.Collection;
+
+public class PlayerManager {
+  HashMap<Player, State> m_playerStates = new HashMap<>();
+
+  public enum State {
+    Idle,
+    Playing,
+    Dead
+  }
+
+  public boolean requestTransitionForAll(State toState) {
+    boolean allSuccess = true;
+    for (Player p : getPlayers()) {
+      allSuccess = allSuccess && requestTransition(p, toState);
+    }
+    return allSuccess;
+  }
+
+  public boolean requestTransition(Player player, State toState) {
+    State currentState = m_playerStates.get(player);
+    if (currentState == toState) {
+      return false;
+    }
+    boolean ret = false;
+    switch(toState) {
+      case Idle:
+        ret = enterIdle(player);break;
+      case Playing:
+        ret = enterPlaying(player);break;
+      case Dead:
+        ret = enterDead(player);break;
+    }
+    if (ret) {
+      m_playerStates.put(player, toState);
+    }
+    return ret;
+  }
+
+  public boolean enterIdle(Player player) {
+    // Reset player to non-game state, return control back to Minecraft
+    player.setGameMode(Bukkit.getDefaultGameMode());
+    return true;
+  }
+
+  // Respawn player
+  public boolean enterPlaying(Player player) {
+    //m_log.fine("Respawning player " + player);
+    player.setGameMode(Bukkit.getDefaultGameMode());
+    player.setHealth(player.getAttribute(Attribute.GENERIC_MAX_HEALTH).getValue());
+    player.setFoodLevel(10);
+    return true;
+  }
+
+  public boolean enterDead(Player player) {
+    //m_log.info("Player has died in game" + player);
+    player.setGameMode(GameMode.SPECTATOR);
+    return true;
+  }
+
+  public void addPlayer(Player player) {
+    //m_log.info("Adding player " + player); 
+    m_playerStates.put(player, State.Idle);
+  }
+
+  public boolean removePlayer(Player player) {
+    //m_log.info("Removing player " + player); 
+    requestTransition(player, State.Idle);
+    m_playerStates.remove(player);
+    return true;
+  }
+
+  public boolean isEmpty() {
+    return m_playerStates.size() == 0;
+  }
+
+  public boolean isAlive(Player player) {
+    return m_playerStates.get(player) == State.Playing;
+  }
+
+  public boolean isAnyoneAlive() {
+    for(Player p : m_playerStates.keySet()) {
+      if (m_playerStates.get(p) == State.Playing) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  public int remainingPlayers() {
+    int aliveCount = 0;
+    for(State s : m_playerStates.values()) {
+      if (s == State.Playing) {
+        aliveCount += 1;
+      }
+    }
+    return aliveCount;
+  }
+
+  Collection<Player> getPlayers() {
+    return m_playerStates.keySet();
+  }
+}
+
diff --git a/src/main/resources/plugin.yml b/src/main/resources/plugin.yml
index 972b0df..663fca6 100644
--- a/src/main/resources/plugin.yml
+++ b/src/main/resources/plugin.yml
@@ -6,7 +6,7 @@ depend:  []
 commands:
   setstage:
     description: Sets a game stage
-  initgame:
+  addplayer:
     description: Adds a player to a game
   debuginfo:
     description: Unknowable powers