diff --git a/.gitignore b/.gitignore
index 80ec311..0a3a6fc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
 node_modules
 
+/app/data
 /.cache
 /build
 .env
diff --git a/app/ecs-components/ecs.js b/app/ecs-components/ecs.js
new file mode 100644
index 0000000..a3ae9ea
--- /dev/null
+++ b/app/ecs-components/ecs.js
@@ -0,0 +1,3 @@
+export default {
+  path: {type: 'string'},
+}
diff --git a/app/ecs-components/index.js b/app/ecs-components/index.js
index 61c6535..3f6fb8d 100644
--- a/app/ecs-components/index.js
+++ b/app/ecs-components/index.js
@@ -1,3 +1,27 @@
+import Arbitrary from '@/ecs/arbitrary.js';
+import Base from '@/ecs/base.js';
+import Schema from '@/ecs/schema.js';
 import gather from '@/engine/gather.js';
 
-export default gather(import.meta.glob('./*.js', {eager: true, import: 'default'}));
+const specificationsOrClasses = gather(
+  import.meta.glob('./*.js', {eager: true, import: 'default'}),
+);
+
+const Components = {};
+for (const name in specificationsOrClasses) {
+  const specificationOrClass = specificationsOrClasses[name];
+  if (specificationOrClass instanceof Base) {
+    Components[name] = specificationOrClass;
+  }
+  else {
+    Components[name] = class Component extends Arbitrary {
+      static name = name;
+      static schema = new Schema({
+        type: 'object',
+        properties: specificationOrClass,
+      });
+    };
+  }
+}
+
+export default Components;
diff --git a/app/ecs-components/world.js b/app/ecs-components/world.js
deleted file mode 100644
index 047d03e..0000000
--- a/app/ecs-components/world.js
+++ /dev/null
@@ -1,3 +0,0 @@
-export default {
-  world: {type: 'uint16'},
-}
diff --git a/app/ecs-systems/index.js b/app/ecs-systems/index.js
new file mode 100644
index 0000000..61c6535
--- /dev/null
+++ b/app/ecs-systems/index.js
@@ -0,0 +1,3 @@
+import gather from '@/engine/gather.js';
+
+export default gather(import.meta.glob('./*.js', {eager: true, import: 'default'}));
diff --git a/app/ecs-systems/update-spatial-hash.js b/app/ecs-systems/update-spatial-hash.js
index 6a96a59..c9602f7 100644
--- a/app/ecs-systems/update-spatial-hash.js
+++ b/app/ecs-systems/update-spatial-hash.js
@@ -54,12 +54,6 @@ class SpatialHash {
 
 export default class UpdateSpatialHash extends System {
 
-  constructor(ecs) {
-    super(ecs);
-    const master = ecs.get(1);
-    this.hash = new SpatialHash(master.AreaSize);
-  }
-
   deindex(entities) {
     super.deindex(entities);
     for (const id of entities) {
@@ -68,6 +62,11 @@ export default class UpdateSpatialHash extends System {
   }
 
   reindex(entities) {
+    for (const id of entities) {
+      if (1 === id) {
+        this.hash = new SpatialHash(this.ecs.get(1).AreaSize);
+      }
+    }
     super.reindex(entities);
     for (const id of entities) {
       this.updateHash(this.ecs.get(id));
diff --git a/app/ecs/arbitrary.test.js b/app/ecs/arbitrary.test.js
index ac59d18..7814478 100644
--- a/app/ecs/arbitrary.test.js
+++ b/app/ecs/arbitrary.test.js
@@ -23,7 +23,8 @@ test('does not serialize default values', () => {
       properties: {foo: {defaultValue: 'bar', type: 'string'}, bar: {type: 'uint8'}},
     });
   }
-  const Component = new CreatingArbitrary();
+  const fakeEcs = {markChange() {}};
+  const Component = new CreatingArbitrary(fakeEcs);
   Component.create(1)
   expect(Component.get(1).toJSON())
     .to.deep.equal({});
diff --git a/app/ecs/base.js b/app/ecs/base.js
index 1250325..24f7d37 100644
--- a/app/ecs/base.js
+++ b/app/ecs/base.js
@@ -1,11 +1,17 @@
 export default class Base {
 
+  ecs;
+
   map = [];
 
   pool = [];
 
   static schema;
 
+  constructor(ecs) {
+    this.ecs = ecs;
+  }
+
   allocateMany(count) {
     const results = [];
     while (count-- > 0 && this.pool.length > 0) {
@@ -54,6 +60,10 @@ export default class Base {
     }
   }
 
+  static gathered(id, key) {
+    this.name = key;
+  }
+
   insertMany(entities) {
     const creating = [];
     for (let i = 0; i < entities.length; i++) {
@@ -71,8 +81,9 @@ export default class Base {
     this.createMany(creating);
   }
 
-  // eslint-disable-next-line no-unused-vars
-  markChange(entityId, components) {}
+  markChange(entityId, key, value) {
+    this.ecs.markChange(entityId, {[this.constructor.name]: {[key]: value}})
+  }
 
   mergeDiff(original, update) {
     return {...original, ...update};
@@ -86,13 +97,4 @@ export default class Base {
     return this.constructor.schema.sizeOf(this.get(entityId));
   }
 
-  static wrap(name, ecs) {
-    class WrappedComponent extends this {
-      markChange(entityId, key, value) {
-        ecs.markChange(entityId, {[name]: {[key]: value}})
-      }
-    }
-    return new WrappedComponent();
-  }
-
 }
diff --git a/app/ecs/component.js b/app/ecs/component.js
deleted file mode 100644
index 285ed0c..0000000
--- a/app/ecs/component.js
+++ /dev/null
@@ -1,14 +0,0 @@
-import Arbitrary from './arbitrary.js';
-import Base from './base.js';
-import Schema from './schema.js';
-
-export default function Component(specificationOrClass) {
-  if (specificationOrClass instanceof Base) {
-    return specificationOrClass;
-  }
-  // Why the rigamarole? Maybe we'll implement a flat component for direct binary storage
-  // eventually.
-  return class AdhocComponent extends Arbitrary {
-    static schema = new Schema({type: 'object', properties: specificationOrClass});
-  };
-}
diff --git a/app/ecs/ecs.js b/app/ecs/ecs.js
index 33b5cef..c7f27c0 100644
--- a/app/ecs/ecs.js
+++ b/app/ecs/ecs.js
@@ -1,7 +1,10 @@
-import Component from './component.js';
 import EntityFactory from './entity-factory.js';
 import Schema from './schema.js';
-import System from './system.js';
+
+import {Encoder, Decoder} from '@msgpack/msgpack';
+
+const decoder = new Decoder();
+const encoder = new Encoder();
 
 export default class Ecs {
 
@@ -9,6 +12,10 @@ export default class Ecs {
 
   diff = {};
 
+  static Systems = {};
+
+  Systems = {};
+
   static Types = {};
 
   Types = {};
@@ -17,19 +24,14 @@ export default class Ecs {
 
   $$entityFactory = new EntityFactory();
 
-  $$systems = [];
-
   constructor() {
-    const {Types} = this.constructor;
-    for (const i in Types) {
-      this.Types[i] = Component(Types[i]).wrap(i, this);
+    const {Systems, Types} = this.constructor;
+    for (const name in Types) {
+      this.Types[name] = new Types[name](this);
+    }
+    for (const name in Systems) {
+      this.Systems[name] = new Systems[name](this);
     }
-  }
-
-  addSystem(source) {
-    const system = System.wrap(source, this);
-    this.$$systems.push(system);
-    system.reindex(this.entities);
   }
 
   apply(patch) {
@@ -88,9 +90,9 @@ export default class Ecs {
     for (let i = 0; i < specificsList.length; i++) {
       const [entityId, components] = specificsList[i];
       const componentKeys = [];
-      for (const key of Object.keys(components)) {
-        if (this.Types[key]) {
-          componentKeys.push(key);
+      for (const name in components) {
+        if (this.Types[name]) {
+          componentKeys.push(name);
         }
       }
       entityIds.push(entityId);
@@ -115,74 +117,29 @@ export default class Ecs {
   }
 
   deindex(entityIds) {
-    for (let i = 0; i < this.$$systems.length; i++) {
-      this.$$systems[i].deindex(entityIds);
+    for (const name in this.Systems) {
+      this.Systems[name].deindex(entityIds);
     }
   }
 
   static deserialize(view) {
     const ecs = new this();
-    let cursor = 0;
-    const headerComponents = view.getUint16(cursor, true);
-    cursor += 2;
-    const keys = [];
-    for (let i = 0; i < headerComponents; ++i) {
-      const wrapped = {value: cursor};
-      keys[i] = Schema.deserialize(view, wrapped, {type: 'string'});
-      cursor = wrapped.value;
+    const types = Object.keys(ecs.Types);
+    const {entities, systems} = decoder.decode(view.buffer);
+    for (const system of systems) {
+      ecs.system(system).active = true;
     }
-    const count = view.getUint32(cursor, true);
-    cursor += 4;
-    const creating = new Map();
-    const updating = new Map();
-    const cursors = new Map();
-    for (let i = 0; i < count; ++i) {
-      const entityId = view.getUint32(cursor, true);
-      if (!ecs.$$entities[entityId]) {
-        creating.set(entityId, {});
-      }
-      cursor += 4;
-      const componentCount = view.getUint16(cursor, true);
-      cursor += 2;
-      cursors.set(entityId, {});
-      const addedComponents = [];
-      for (let j = 0; j < componentCount; ++j) {
-        const componentId = view.getUint16(cursor, true);
-        cursor += 2;
-        const component = keys[componentId];
-        const componentSize = view.getUint32(cursor, true);
-        cursor += 4;
-        if (!this.Types[component]) {
-          console.error(`can't deserialize nonexistent component ${component}`);
-          cursor += componentSize;
-          continue;
-        }
-        if (!ecs.$$entities[entityId]) {
-          creating.get(entityId)[component] = false;
-        }
-        else if (!ecs.$$entities[entityId].constructor.types.includes(component)) {
-          addedComponents.push(component);
-          if (!updating.has(component)) {
-            updating.set(component, []);
-          }
-          updating.get(component).push([entityId, false]);
-        }
-        cursors.get(entityId)[component] = cursor;
-        cursor += componentSize;
-      }
-      if (addedComponents.length > 0 && ecs.$$entities[entityId]) {
-        ecs.rebuild(entityId, (types) => types.concat(addedComponents));
-      }
-    }
-    ecs.createManySpecific(Array.from(creating.entries()));
-    for (const [component, entityIds] of updating) {
-      ecs.Types[component].createMany(entityIds);
-    }
-    for (const [entityId, components] of cursors) {
-      for (const component in components) {
-        ecs.Types[component].deserialize(entityId, view, components[component]);
-      }
+    const specifics = [];
+    let max = 1;
+    for (const id in entities) {
+      max = Math.max(max, parseInt(id));
+      specifics.push([
+        parseInt(id),
+        Object.fromEntries(Object.entries(entities[id]).filter(([type]) => types.includes(type))),
+      ]);
     }
+    ecs.$$caret = max + 1;
+    ecs.createManySpecific(specifics);
     return ecs;
   }
 
@@ -272,21 +229,21 @@ export default class Ecs {
     // Created?
     else if (!this.diff[entityId]) {
       const filtered = {};
-      for (const type in components) {
-        filtered[type] = false === components[type]
+      for (const name in components) {
+        filtered[name] = false === components[name]
           ? false
-          : this.Types[type].constructor.filterDefaults(components[type]);
+          : this.Types[name].constructor.filterDefaults(components[name]);
       }
       this.diff[entityId] = filtered;
     }
     // Otherwise, merge.
     else {
-      for (const type in components) {
-        this.diff[entityId][type] = false === components[type]
+      for (const name in components) {
+        this.diff[entityId][name] = false === components[name]
           ? false
-          : this.Types[type].mergeDiff(
-            this.diff[entityId][type] || {},
-            components[type],
+          : this.Types[name].mergeDiff(
+            this.diff[entityId][name] || {},
+            components[name],
           );
       }
     }
@@ -302,8 +259,8 @@ export default class Ecs {
   }
 
   reindex(entityIds) {
-    for (let i = 0; i < this.$$systems.length; i++) {
-      this.$$systems[i].reindex(entityIds);
+    for (const name in this.Systems) {
+      this.Systems[name].reindex(entityIds);
     }
   }
 
@@ -333,49 +290,12 @@ export default class Ecs {
     this.reindex(unique.values());
   }
 
-  removeSystem(SystemLike) {
-    const index = this.$$systems.findIndex((system) => SystemLike === system.source);
-    if (-1 !== index) {
-      this.$$systems.splice(index, 1);
-    }
-  }
-
   static serialize(ecs, view) {
+    const buffer = encoder.encode(ecs.toJSON());
     if (!view) {
-      view = new DataView(new ArrayBuffer(ecs.size()));
+      view = new DataView(new ArrayBuffer(buffer.length));
     }
-    let cursor = 0;
-    const keys = Object.keys(ecs.Types);
-    view.setUint16(cursor, keys.length, true);
-    cursor += 2;
-    for (const i in keys) {
-      cursor += Schema.serialize(keys[i], view, cursor, {type: 'string'});
-    }
-    const entitiesWrittenAt = cursor;
-    let entitiesWritten = 0;
-    cursor += 4;
-    for (const entityId of ecs.entities) {
-      const entity = ecs.get(entityId);
-      entitiesWritten += 1;
-      view.setUint32(cursor, entityId, true);
-      cursor += 4;
-      const entityComponents = entity.constructor.types;
-      view.setUint16(cursor, entityComponents.length, true);
-      const componentsWrittenAt = cursor;
-      cursor += 2;
-      for (const component of entityComponents) {
-        const instance = ecs.Types[component];
-        view.setUint16(cursor, keys.indexOf(component), true);
-        cursor += 2;
-        const sizeOf = instance.sizeOf(entityId);
-        view.setUint32(cursor, sizeOf, true);
-        cursor += 4;
-        instance.serialize(entityId, view, cursor);
-        cursor += sizeOf;
-      }
-      view.setUint16(componentsWrittenAt, entityComponents.length, true);
-    }
-    view.setUint32(entitiesWrittenAt, entitiesWritten, true);
+    (new Uint8Array(view.buffer)).set(buffer);
     return view;
   }
 
@@ -398,31 +318,55 @@ export default class Ecs {
     return size;
   }
 
-  system(SystemLike) {
-    return this.$$systems.find((system) => SystemLike === system.source)
+  system(name) {
+    return this.Systems[name];
   }
 
   tick(elapsed) {
-    for (let i = 0; i < this.$$systems.length; i++) {
-      this.$$systems[i].tick(elapsed);
+    for (const name in this.Systems) {
+      if (this.Systems[name].active) {
+        this.Systems[name].tick(elapsed);
+      }
     }
-    for (let i = 0; i < this.$$systems.length; i++) {
-      this.$$systems[i].finalize(elapsed);
+    for (const name in this.Systems) {
+      if (this.Systems[name].active) {
+        this.Systems[name].finalize(elapsed);
+      }
     }
     this.tickDestruction();
   }
 
   tickDestruction() {
     const unique = new Set();
-    for (let i = 0; i < this.$$systems.length; i++) {
-      for (let j = 0; j < this.$$systems[i].destroying.length; j++) {
-        unique.add(this.$$systems[i].destroying[j]);
+    for (const name in this.Systems) {
+      const System = this.Systems[name];
+      if (System.active) {
+        for (let j = 0; j < System.destroying.length; j++) {
+          unique.add(System.destroying[j]);
+        }
+        System.tickDestruction();
       }
-      this.$$systems[i].tickDestruction();
     }
     if (unique.size > 0) {
       this.destroyMany(unique.values());
     }
   }
 
+  toJSON() {
+    const entities = {};
+    for (const id in this.$$entities) {
+      entities[id] = this.$$entities[id].toJSON();
+    }
+    const systems = [];
+    for (const name in this.Systems) {
+      if (this.Systems[name].active) {
+        systems.push(name);
+      }
+    }
+    return {
+      entities,
+      systems,
+    };
+  }
+
 }
diff --git a/app/ecs/ecs.test.js b/app/ecs/ecs.test.js
index 231cc7e..a9fc57e 100644
--- a/app/ecs/ecs.test.js
+++ b/app/ecs/ecs.test.js
@@ -1,41 +1,66 @@
-import {expect, test, vi} from 'vitest';
+import {expect, test} from 'vitest';
 
+import Arbitrary from './arbitrary.js';
 import Ecs from './ecs.js';
+import Schema from './schema.js';
 import System from './system.js';
 
-const Empty = {};
+function wrapSpecification(name, specification) {
+  return class Component extends Arbitrary {
+    static name = name;
+    static schema = new Schema({
+      type: 'object',
+      properties: specification,
+    });
+  };
+}
 
-const Name = {
+const Empty = wrapSpecification('Empty', {});
+
+const Name = wrapSpecification('Name', {
   name: {type: 'string'},
-};
+});
 
-const Position = {
+const Position = wrapSpecification('Position', {
   x: {type: 'int32', defaultValue: 32},
   y: {type: 'int32'},
   z: {type: 'int32'},
-};
+});
 
-test('adds and remove systems at runtime', () => {
-  const ecs = new Ecs();
+test('activates and deactivates systems at runtime', () => {
   let oneCount = 0;
   let twoCount = 0;
-  const oneSystem = () => {
-    oneCount++;
-  };
-  ecs.addSystem(oneSystem);
+  class SystemToggle extends Ecs {
+    static Systems = {
+      OneSystem: class extends System {
+        tick() {
+          oneCount += 1;
+        }
+      },
+      TwoSystem: class extends System {
+        tick() {
+          twoCount += 1;
+        }
+      },
+    }
+  }
+  const ecs = new SystemToggle();
+  ecs.tick();
+  expect(oneCount)
+    .to.equal(0);
+  expect(twoCount)
+    .to.equal(0);
+  ecs.system('OneSystem').active = true;
   ecs.tick();
   expect(oneCount)
     .to.equal(1);
-  const twoSystem = () => {
-    twoCount++;
-  };
-  ecs.addSystem(twoSystem);
+  ecs.system('TwoSystem').active = true;
   ecs.tick();
   expect(oneCount)
     .to.equal(2);
   expect(twoCount)
     .to.equal(1);
-  ecs.removeSystem(oneSystem);
+  ecs.system('OneSystem').active = false;
   ecs.tick();
   expect(oneCount)
     .to.equal(2);
@@ -108,33 +133,35 @@ test('inserts components into entities', () => {
 });
 
 test('ticks systems', () => {
-  const Momentum = {
+  const Momentum = wrapSpecification('Momentum', {
     x: {type: 'int32'},
     y: {type: 'int32'},
     z: {type: 'int32'},
-  };
+  });
   class TickEcs extends Ecs {
+    static Systems = {
+      Physics: class Physics extends System {
+
+        static queries() {
+          return {
+            default: ['Position', 'Momentum'],
+          };
+        }
+
+        tick(elapsed) {
+          for (const [position, momentum] of this.select('default')) {
+            position.x += momentum.x * elapsed;
+            position.y += momentum.y * elapsed;
+            position.z += momentum.z * elapsed;
+          }
+        }
+
+      },
+    }
     static Types = {Momentum, Position};
   }
   const ecs = new TickEcs();
-  class Physics extends System {
-
-    static queries() {
-      return {
-        default: ['Position', 'Momentum'],
-      };
-    }
-
-    tick(elapsed) {
-      for (const [position, momentum] of this.select('default')) {
-        position.x += momentum.x * elapsed;
-        position.y += momentum.y * elapsed;
-        position.z += momentum.z * elapsed;
-      }
-    }
-
-  }
-  ecs.addSystem(Physics);
+  ecs.system('Physics').active = true;
   const entity = ecs.create({Momentum: {}, Position: {y: 128}});
   const position = JSON.stringify(ecs.get(entity).Position);
   ecs.tick(1);
@@ -147,13 +174,17 @@ test('ticks systems', () => {
 });
 
 test('creates many entities when ticking systems', () => {
-  const ecs = new Ecs();
-  class Spawn extends System {
-    tick() {
-      this.createManyEntities(Array.from({length: 5}).map(() => []));
-    }
+  class TickingSystemEcs extends Ecs {
+    static Systems = {
+      Spawn: class extends System {
+        tick() {
+          this.createManyEntities(Array.from({length: 5}).map(() => []));
+        }
+      },
+    };
   }
-  ecs.addSystem(Spawn);
+  const ecs = new TickingSystemEcs();
+  ecs.system('Spawn').active = true;
   ecs.create();
   expect(ecs.get(5))
     .to.be.undefined;
@@ -163,13 +194,17 @@ test('creates many entities when ticking systems', () => {
 });
 
 test('creates entities when ticking systems', () => {
-  const ecs = new Ecs();
-  class Spawn extends System {
-    tick() {
-      this.createEntity();
-    }
+  class TickingSystemEcs extends Ecs {
+    static Systems = {
+      Spawn: class extends System {
+        tick() {
+          this.createEntity();
+        }
+      },
+    };
   }
-  ecs.addSystem(Spawn);
+  const ecs = new TickingSystemEcs();
+  ecs.system('Spawn').active = true;
   ecs.create();
   expect(ecs.get(2))
     .to.be.undefined;
@@ -179,20 +214,21 @@ test('creates entities when ticking systems', () => {
 });
 
 test('schedules entities to be deleted when ticking systems', () => {
-  const ecs = new Ecs();
   let entity;
-  class Despawn extends System {
-
-    finalize() {
-      entity = ecs.get(1);
-    }
-
-    tick() {
-      this.destroyEntity(1);
-    }
-
+  class TickingSystemEcs extends Ecs {
+    static Systems = {
+      Despawn: class extends System {
+        finalize() {
+          entity = ecs.get(1);
+        }
+        tick() {
+          this.destroyEntity(1);
+        }
+      },
+    };
   }
-  ecs.addSystem(Despawn);
+  const ecs = new TickingSystemEcs();
+  ecs.system('Despawn').active = true;
   ecs.create();
   ecs.tick(1);
   expect(entity)
@@ -202,46 +238,48 @@ test('schedules entities to be deleted when ticking systems', () => {
 });
 
 test('adds components to and remove components from entities when ticking systems', () => {
-  class TickingEcs extends Ecs {
-    static Types = {Foo: {bar: {type: 'uint8'}}};
-  }
-  const ecs = new TickingEcs();
   let addLength, removeLength;
-  class AddComponent extends System {
-    static queries() {
-      return {
-        default: ['Foo'],
-      };
-    }
-    tick() {
-      this.insertComponents(1, {Foo: {}});
-    }
-    finalize() {
-      addLength = Array.from(this.select('default')).length;
-    }
+  class TickingSystemEcs extends Ecs {
+    static Systems = {
+      AddComponent: class extends System {
+        static queries() {
+          return {
+            default: ['Foo'],
+          };
+        }
+        tick() {
+          this.insertComponents(1, {Foo: {}});
+        }
+        finalize() {
+          addLength = Array.from(this.select('default')).length;
+        }
+      },
+      RemoveComponent: class extends System {
+        static queries() {
+          return {
+            default: ['Foo'],
+          };
+        }
+        tick() {
+          this.removeComponents(1, ['Foo']);
+        }
+        finalize() {
+          removeLength = Array.from(this.select('default')).length;
+        }
+      },
+    };
+    static Types = {Foo: wrapSpecification('Foo', {bar: {type: 'uint8'}})};
   }
-  class RemoveComponent extends System {
-    static queries() {
-      return {
-        default: ['Foo'],
-      };
-    }
-    tick() {
-      this.removeComponents(1, ['Foo']);
-    }
-    finalize() {
-      removeLength = Array.from(this.select('default')).length;
-    }
-  }
-  ecs.addSystem(AddComponent);
+  const ecs = new TickingSystemEcs();
+  ecs.system('AddComponent').active = true;
   ecs.create();
   ecs.tick(1);
   expect(addLength)
     .to.equal(1);
   expect(ecs.get(1).Foo)
     .to.not.be.undefined;
-  ecs.removeSystem(AddComponent);
-  ecs.addSystem(RemoveComponent);
+  ecs.system('AddComponent').active = false;
+  ecs.system('RemoveComponent').active = true;
   ecs.tick(1);
   expect(removeLength)
     .to.equal(0);
@@ -412,35 +450,25 @@ test('serializes and deserializes', () => {
   class SerializingEcs extends Ecs {
     static Types = {Empty, Name, Position};
   }
-  // # of components + strings (Empty,  Name,   Position)
-  // 2               +          4 + 5 + 4 + 4 + 4 + 8     = 31
   const ecs = new SerializingEcs();
-  // ID + # of components + Empty + Position + x + y + z
-  // 4  + 2               + 2 + 4 + 2 + 4    + 4 + 4 + 4 = 30
   ecs.createSpecific(1, {Empty: {}, Position: {x: 64}});
-  // ID + # of components + Name  + 'foobar' + Position + x + y + z
-  // 4  + 2               + 2 + 4 + 4 + 6    + 2 + 4    + 4 + 4 + 4 = 40
   ecs.createSpecific(16, {Name: {name: 'foobar'}, Position: {x: 128}});
+  expect(ecs.toJSON())
+    .to.deep.equal({
+      entities: {
+        1: {Empty: {}, Position: {x: 64}},
+        16: {Name: {name: 'foobar'}, Position: {x: 128}},
+      },
+      systems: [],
+    });
   const view = SerializingEcs.serialize(ecs);
-  // # of entities + Header + Entity(1) + Entity(16)
-  // 4             + 31     + 30        + 40         = 105
-  expect(view.byteLength)
-    .to.equal(105);
-  // Entity values.
-  expect(view.getUint32(4 + 31 + 30 - 12, true))
-    .to.equal(64);
-  expect(view.getUint32(4 + 31 + 30 + 40 - 12, true))
-    .to.equal(128);
   const deserialized = SerializingEcs.deserialize(view);
-  // # of entities.
   expect(Array.from(deserialized.entities).length)
     .to.equal(2);
-  // Composition of entities.
   expect(deserialized.get(1).constructor.types)
     .to.deep.equal(['Empty', 'Position']);
   expect(deserialized.get(16).constructor.types)
     .to.deep.equal(['Name', 'Position']);
-  // Entity values.
   expect(JSON.stringify(deserialized.get(1)))
     .to.equal(JSON.stringify({Empty: {}, Position: {x: 64}}))
   expect(JSON.stringify(deserialized.get(1).Position))
@@ -462,22 +490,9 @@ test('deserializes from compatible ECS', () => {
   ecs.createSpecific(1, {Empty: {}, Position: {x: 64}});
   ecs.createSpecific(16, {Name: {name: 'foobar'}, Position: {x: 128}});
   const view = SerializingEcs.serialize(ecs);
-  const consoleErrorSpy = vi.spyOn(console, 'error').mockImplementation(() => {});
   const deserialized = DeserializingEcs.deserialize(view);
-  expect(consoleErrorSpy.mock.calls.length)
-    .to.equal(2);
-  consoleErrorSpy.mockRestore();
   expect(deserialized.get(1).toJSON())
     .to.deep.equal({Empty: {}});
   expect(deserialized.get(16).toJSON())
     .to.deep.equal({Name: {name: 'foobar'}});
 });
-
-test('deserializes empty', () => {
-  class SerializingEcs extends Ecs {
-    static Types = {Empty, Name, Position};
-  }
-  const ecs = SerializingEcs.deserialize(new DataView(new Uint16Array([0, 0, 0]).buffer));
-  expect(ecs)
-    .to.not.be.undefined;
-});
diff --git a/app/ecs/query.test.js b/app/ecs/query.test.js
index 565a793..13614f7 100644
--- a/app/ecs/query.test.js
+++ b/app/ecs/query.test.js
@@ -1,11 +1,22 @@
 import {expect, test} from 'vitest';
 
-import Component from './component.js';
+import Arbitrary from './arbitrary.js';
 import Query from './query.js';
+import Schema from './schema.js';
 
-const A = new (Component({a: {type: 'int32', defaultValue: 420}}));
-const B = new (Component({b: {type: 'int32', defaultValue: 69}}));
-const C = new (Component({c: {type: 'int32'}}));
+function wrapSpecification(name, specification) {
+  return class Component extends Arbitrary {
+    static name = name;
+    static schema = new Schema({
+      type: 'object',
+      properties: specification,
+    });
+  };
+}
+
+const A = new (wrapSpecification('A', {a: {type: 'int32', defaultValue: 420}}));
+const B = new (wrapSpecification('B', {b: {type: 'int32', defaultValue: 69}}));
+const C = new (wrapSpecification('C', {c: {type: 'int32'}}));
 
 const Types = {A, B, C};
 Types.A.createMany([[2], [3]]);
@@ -50,7 +61,7 @@ test('can deindex', () => {
 });
 
 test('can reindex', () => {
-  const Test = new (Component({a: {type: 'int32', defaultValue: 420}}));
+  const Test = new (wrapSpecification('Test', {a: {type: 'int32', defaultValue: 420}}));
   Test.createMany([[2], [3]]);
   const query = new Query(['Test'], {Test});
   query.reindex([2, 3]);
diff --git a/app/ecs/system.js b/app/ecs/system.js
index 55dc8f1..ff9bea2 100644
--- a/app/ecs/system.js
+++ b/app/ecs/system.js
@@ -3,6 +3,8 @@ import Query from './query.js';
 
 export default class System {
 
+  active = false;
+
   destroying = [];
 
   ecs;
@@ -15,6 +17,15 @@ export default class System {
     for (const i in queries) {
       this.queries[i] = new Query(queries[i], ecs.Types);
     }
+    this.reindex(ecs.entities);
+  }
+
+  createEntity(components) {
+    return this.ecs.create(components);
+  }
+
+  createManyEntities(componentsList) {
+    return this.ecs.createMany(componentsList);
   }
 
   deindex(entityIds) {
@@ -35,17 +46,12 @@ export default class System {
 
   finalize() {}
 
-  static normalize(SystemLike) {
-    if (SystemLike.prototype instanceof System) {
-      return SystemLike;
-    }
-    if ('function' === typeof SystemLike) {
-      class TickingSystem extends System {}
-      TickingSystem.prototype.tick = SystemLike;
-      return TickingSystem;
-    }
-    /* v8 ignore next */
-    throw new TypeError(`Couldn't normalize '${SystemLike}' as a system`);
+  insertComponents(entityId, components) {
+    this.ecs.insert(entityId, components);
+  }
+
+  insertManyComponents(components) {
+    this.ecs.insertMany(components);
   }
 
   static queries() {
@@ -58,6 +64,14 @@ export default class System {
     }
   }
 
+  removeComponents(entityId, components) {
+    this.ecs.remove(entityId, components);
+  }
+
+  removeManyComponents(entityIds) {
+    this.ecs.removeMany(entityIds);
+  }
+
   select(query) {
     return this.queries[query].select();
   }
@@ -69,44 +83,4 @@ export default class System {
 
   tick() {}
 
-  static wrap(source, ecs) {
-    class WrappedSystem extends System.normalize(source) {
-
-      constructor() {
-        super(ecs);
-        this.reindex(ecs.entities);
-      }
-
-      createEntity(components) {
-        return this.ecs.create(components);
-      }
-
-      createManyEntities(componentsList) {
-        return this.ecs.createMany(componentsList);
-      }
-
-      get source() {
-        return source;
-      }
-
-      insertComponents(entityId, components) {
-        this.ecs.insert(entityId, components);
-      }
-
-      insertManyComponents(components) {
-        this.ecs.insertMany(components);
-      }
-
-      removeComponents(entityId, components) {
-        this.ecs.remove(entityId, components);
-      }
-
-      removeManyComponents(entityIds) {
-        this.ecs.removeMany(entityIds);
-      }
-
-    }
-    return new WrappedSystem();
-  }
-
 }
diff --git a/app/engine/ecs.js b/app/engine/ecs.js
index 89ee425..9ec4c60 100644
--- a/app/engine/ecs.js
+++ b/app/engine/ecs.js
@@ -1,7 +1,9 @@
 import Ecs from '@/ecs/ecs.js';
+import Systems from '@/ecs-systems/index.js';
 import Types from '@/ecs-components/index.js';
 
 class EngineEcs extends Ecs {
+  static Systems = Systems;
   static Types = Types;
 }
 
diff --git a/app/engine/engine.js b/app/engine/engine.js
index c2bd099..72314ce 100644
--- a/app/engine/engine.js
+++ b/app/engine/engine.js
@@ -1,38 +1,12 @@
+import {join} from 'node:path';
+
 import {
   MOVE_MAP,
   TPS,
 } from '@/constants.js';
-import ControlMovement from '@/ecs-systems/control-movement.js';
-import ApplyMomentum from '@/ecs-systems/apply-momentum.js';
-import CalculateAabbs from '@/ecs-systems/calculate-aabbs.js';
-import ClampPositions from '@/ecs-systems/clamp-positions.js';
-import FollowCamera from '@/ecs-systems/follow-camera.js';
-import UpdateSpatialHash from '@/ecs-systems/update-spatial-hash.js';
-import RunAnimations from '@/ecs-systems/run-animations.js';
-import ControlDirection from '@/ecs-systems/control-direction.js';
-import SpriteDirection from '@/ecs-systems/sprite-direction.js';
 import Ecs from '@/engine/ecs.js';
 import {decode, encode} from '@/packets/index.js';
 
-const players = {
-  0: {
-    Camera: {},
-    Controlled: {up: 0, right: 0, down: 0, left: 0},
-    Direction: {direction: 2},
-    Momentum: {},
-    Position: {x: 368, y: 368},
-    VisibleAabb: {},
-    World: {world: 1},
-    Sprite: {
-      animation: 'moving:down',
-      frame: 0,
-      frames: 8,
-      source: '/assets/dude.json',
-      speed: 0.115,
-    },
-  },
-};
-
 export default class Engine {
 
   incomingActions = [];
@@ -50,9 +24,7 @@ export default class Engine {
   server;
 
   constructor(Server) {
-    this.ecses = {
-      1: this.createHomestead(),
-    };
+    this.ecses = {};
     class SilphiusServer extends Server {
       accept(connection, packed) {
         super.accept(connection, decode(packed));
@@ -67,38 +39,28 @@ export default class Engine {
     });
   }
 
-  async connectPlayer(connection) {
-    this.connections.push(connection);
-    const entityJson = await this.loadPlayer(connection);
-    const ecs = this.ecses[entityJson.World.world];
+  async connectPlayer(connection, id) {
+    const entityJson = await this.loadPlayer(id);
+    if (!this.ecses[entityJson.Ecs.path]) {
+      await this.loadEcs(entityJson.Ecs.path);
+    }
+    const ecs = this.ecses[entityJson.Ecs.path];
     const entity = ecs.create(entityJson);
+    this.connections.push(connection);
     this.connectedPlayers.set(
       connection,
       {
         entity: ecs.get(entity),
+        id,
         memory: new Set(),
       },
     );
   }
 
-  createEcs(master) {
+  createEcs() {
     const ecs = new Ecs();
-    ecs.create(master);
-    ecs.addSystem(ControlMovement);
-    ecs.addSystem(ApplyMomentum);
-    ecs.addSystem(ClampPositions);
-    ecs.addSystem(FollowCamera);
-    ecs.addSystem(CalculateAabbs);
-    ecs.addSystem(UpdateSpatialHash);
-    ecs.addSystem(ControlDirection);
-    ecs.addSystem(SpriteDirection);
-    ecs.addSystem(RunAnimations);
-    return ecs;
-  }
-
-  createHomestead() {
     const area = {x: 100, y: 60};
-    return this.createEcs({
+    ecs.create({
       AreaSize: {x: area.x * 16, y: area.y * 16},
       TileLayers: {
         layers: [
@@ -111,12 +73,61 @@ export default class Engine {
         ],
       },
     });
+    const defaultSystems = [
+      'ControlMovement',
+      'ApplyMomentum',
+      'ClampPositions',
+      'FollowCamera',
+      'CalculateAabbs',
+      'UpdateSpatialHash',
+      'ControlDirection',
+      'SpriteDirection',
+      'RunAnimations',
+    ];
+    defaultSystems.forEach((defaultSystem) => {
+      ecs.system(defaultSystem).active = true;
+    });
+    return ecs;
   }
 
-  disconnectPlayer(connection) {
-    const {entity} = this.connectedPlayers.get(connection);
-    const ecs = this.ecses[entity.World.world];
-    players[0] = JSON.parse(JSON.stringify(entity.toJSON()));
+  async createHomestead(id) {
+    const ecs = this.createEcs();
+    const view = Ecs.serialize(ecs);
+    await this.server.writeData(
+      join('homesteads', `${id}`),
+      view,
+    );
+  }
+
+  async createPlayer(id) {
+    const player = {
+      Camera: {},
+      Controlled: {up: 0, right: 0, down: 0, left: 0},
+      Direction: {direction: 2},
+      Ecs: {path: join('homesteads', `${id}`)},
+      Momentum: {},
+      Position: {x: 368, y: 368},
+      VisibleAabb: {},
+      Sprite: {
+        animation: 'moving:down',
+        frame: 0,
+        frames: 8,
+        source: '/assets/dude.json',
+        speed: 0.115,
+      },
+    };
+    const buffer = (new TextEncoder()).encode(JSON.stringify(player));
+    await this.server.writeData(
+      join('players', `${id}`),
+      buffer,
+    );
+    return buffer;
+  }
+
+  async disconnectPlayer(connection) {
+    const {entity, id} = this.connectedPlayers.get(connection);
+    const ecs = this.ecses[entity.Ecs.path];
+    await this.savePlayer(id, entity);
     ecs.destroy(entity.id);
     this.connectedPlayers.delete(connection);
     this.connections.splice(this.connections.indexOf(connection), 1);
@@ -125,8 +136,29 @@ export default class Engine {
   async load() {
   }
 
-  async loadPlayer() {
-    return players[0];
+  async loadEcs(path) {
+    this.ecses[path] = Ecs.deserialize(await this.server.readData(path));
+  }
+
+  async loadPlayer(id) {
+    let buffer;
+    try {
+      buffer = await this.server.readData(['players', `${id}`].join('/'))
+    }
+    catch (error) {
+      if ('ENOENT' !== error.code) {
+        throw error;
+      }
+      await this.createHomestead(id);
+      buffer = await this.createPlayer(id);
+    }
+    return JSON.parse((new TextDecoder()).decode(buffer));
+  }
+
+  async savePlayer(id, entity) {
+    const encoder = new TextEncoder();
+    const buffer = encoder.encode(JSON.stringify(entity.toJSON()));
+    await this.server.writeData(['players', `${id}`].join('/'), buffer);
   }
 
   start() {
@@ -174,8 +206,8 @@ export default class Engine {
     const update = {};
     const {entity, memory} = this.connectedPlayers.get(connection);
     const mainEntityId = entity.id;
-    const ecs = this.ecses[entity.World.world];
-    const nearby = ecs.system(UpdateSpatialHash).nearby(entity);
+    const ecs = this.ecses[entity.Ecs.path];
+    const nearby = ecs.system('UpdateSpatialHash').nearby(entity);
     // Master entity.
     nearby.add(ecs.get(1));
     const lastMemory = new Set(memory.values());
diff --git a/app/engine/engine.test.js b/app/engine/engine.test.js
index 944b38c..350c7a2 100644
--- a/app/engine/engine.test.js
+++ b/app/engine/engine.test.js
@@ -2,28 +2,41 @@ import {expect, test} from 'vitest';
 
 import {RESOLUTION} from '@/constants.js'
 import Server from '@/net/server/server.js';
+
 import Engine from './engine.js';
 
 test('visibility-based updates', async () => {
   const engine = new Engine(Server);
-  const ecs = engine.ecses[1];
+  const data = {};
+  engine.server.readData = async (path) => {
+    if (path in data) {
+      return data[path];
+    }
+    const error = new Error();
+    error.code = 'ENOENT';
+    throw error;
+  };
+  engine.server.writeData = async (path, view) => {
+    data[path] = view;
+  };
+  // Connect an entity.
+  await engine.connectPlayer(0, 0);
+  const ecs = engine.ecses['homesteads/0'];
   // Create an entity.
   const entity = ecs.get(ecs.create({
     Momentum: {x: 1, y: 0},
     Position: {x: (RESOLUTION.x * 1.5) + 32 - 3, y: 20},
     VisibleAabb: {},
   }));
-  // Connect an entity.
-  await engine.connectPlayer(undefined);
   // Tick and get update. Should be a full update.
   engine.tick(1);
-  expect(engine.updateFor(undefined))
-    .to.deep.include({2: ecs.get(2).toJSON(), 3: {MainEntity: {}, ...ecs.get(3).toJSON()}});
+  expect(engine.updateFor(0))
+    .to.deep.include({2: {MainEntity: {}, ...ecs.get(2).toJSON()}, 3: ecs.get(3).toJSON()});
   // Tick and get update. Should be a partial update.
   engine.tick(1);
-  expect(engine.updateFor(undefined))
+  expect(engine.updateFor(0))
     .to.deep.include({
-      2: {
+      3: {
         Position: {x: (RESOLUTION.x * 1.5) + 32 - 1},
         VisibleAabb: {
           x0: 1199,
@@ -33,11 +46,11 @@ test('visibility-based updates', async () => {
     });
   // Tick and get update. Should remove the entity.
   engine.tick(1);
-  expect(engine.updateFor(undefined))
-    .to.deep.include({2: false});
+  expect(engine.updateFor(0))
+    .to.deep.include({3: false});
   // Aim back toward visible area and tick. Should be a full update for that entity.
   entity.Momentum.x = -1;
   engine.tick(1);
-  expect(engine.updateFor(undefined))
-    .to.deep.include({2: ecs.get(2).toJSON()});
+  expect(engine.updateFor(0))
+    .to.deep.include({3: ecs.get(3).toJSON()});
 });
diff --git a/app/net/server/worker.js b/app/net/server/worker.js
index d953825..c9a48c9 100644
--- a/app/net/server/worker.js
+++ b/app/net/server/worker.js
@@ -16,7 +16,7 @@ onmessage = (event) => {
 (async () => {
   await engine.load();
   engine.start();
-  await engine.connectPlayer(undefined);
+  await engine.connectPlayer();
   postMessage(encode({type: 'ConnectionStatus', payload: 'connected'}));
 })();
 
diff --git a/app/routes/_main-menu.play.$.$/route.jsx b/app/routes/_main-menu.play.$.$/route.jsx
index 51ca82b..3dbf0b6 100644
--- a/app/routes/_main-menu.play.$.$/route.jsx
+++ b/app/routes/_main-menu.play.$.$/route.jsx
@@ -1,8 +1,15 @@
+import {json} from "@remix-run/node";
 import {useEffect, useState} from 'react';
 import {useOutletContext, useParams} from 'react-router-dom';
 
 import ClientContext from '@/context/client.js';
 import Ui from '@/react-components/ui.jsx';
+import {juggleSession} from '@/session.server';
+
+export async function loader({request}) {
+  await juggleSession(request);
+  return json({});
+}
 
 export default function PlaySpecific() {
   const Client = useOutletContext();
diff --git a/app/session.server.js b/app/session.server.js
new file mode 100644
index 0000000..6bd8086
--- /dev/null
+++ b/app/session.server.js
@@ -0,0 +1,34 @@
+import {join} from 'node:path';
+
+import {createFileSessionStorage} from "@remix-run/node";
+import {redirect} from '@remix-run/react';
+
+const {getSession, commitSession, destroySession} = createFileSessionStorage({
+  dir: join(import.meta.dirname, 'data', 'remote', 'sessions'),
+  cookie: {
+    secrets: ["r3m1xr0ck5"],
+    sameSite: true,
+  },
+});
+
+export {getSession, commitSession, destroySession};
+
+export async function juggleSession(request) {
+  const session = await getSession(request.headers.get('Cookie'));
+  const url = new URL(request.url);
+  if (!session.get('id')) {
+    if (!url.searchParams.has('session')) {
+      const [id] = crypto.getRandomValues(new Uint32Array(1));
+      session.set('id', id);
+      throw redirect(`${url.origin}${url.pathname}?session`, {
+        headers: {
+          'Set-Cookie': await commitSession(session),
+        },
+      });
+    }
+  }
+  else if (url.searchParams.has('session')) {
+    throw redirect(`${url.origin}${url.pathname}`);
+  }
+  return session ? session : {id: 0};
+}
diff --git a/app/websocket.js b/app/websocket.js
index 795ade8..98012e6 100644
--- a/app/websocket.js
+++ b/app/websocket.js
@@ -1,7 +1,12 @@
+import {mkdir, readFile, writeFile} from 'node:fs/promises';
+import {dirname, join} from 'node:path';
+
 import {WebSocketServer} from 'ws';
 
+import Server from '@/net/server/server.js';
+import {getSession} from '@/session.server.js';
+
 import Engine from './engine/engine.js';
-import Server from './net/server/server.js';
 
 const wss = new WebSocketServer({
   noServer: true,
@@ -23,19 +28,36 @@ let engine;
 let onConnect;
 
 function createOnConnect(engine) {
-  onConnect = async (ws) => {
-    ws.on('close', () => {
-      engine.disconnectPlayer(ws);
+  onConnect = async (ws, request) => {
+    ws.on('close', async () => {
+      await engine.disconnectPlayer(ws);
     })
     ws.on('message', (packed) => {
       engine.server.accept(ws, new DataView(packed.buffer, packed.byteOffset, packed.length));
     });
-    await engine.connectPlayer(ws);
+    const session = await getSession(request.headers['cookie']);
+    await engine.connectPlayer(ws, session.get('id'));
   };
   wss.on('connection', onConnect);
 }
 
 class SocketServer extends Server {
+  async ensurePath(path) {
+    await mkdir(path, {recursive: true});
+  }
+  static qualify(path) {
+    return join(import.meta.dirname, 'data', 'remote', 'UNIVERSE', path);
+  }
+  async readData(path) {
+    const qualified = this.constructor.qualify(path);
+    await this.ensurePath(dirname(qualified));
+    return readFile(qualified);
+  }
+  async writeData(path, view) {
+    const qualified = this.constructor.qualify(path);
+    await this.ensurePath(dirname(qualified));
+    await writeFile(qualified, view);
+  }
   transmit(ws, packed) { ws.send(packed); }
 }
 
diff --git a/package.json b/package.json
index 46b52ed..7bf0748 100644
--- a/package.json
+++ b/package.json
@@ -9,7 +9,8 @@
     "lint": "eslint --ignore-path .gitignore --cache --cache-location ./node_modules/.cache/eslint .",
     "start": "cross-env NODE_ENV=production node ./server.js",
     "storybook": "storybook dev -p 6006",
-    "storybook:build": "storybook build"
+    "storybook:build": "storybook build",
+    "test": "vitest app"
   },
   "dependencies": {
     "@msgpack/msgpack": "^3.0.0-beta2",