diff --git a/packages/ecs/src/component.js b/packages/ecs/src/component.js
index 0013927..c5a0b93 100644
--- a/packages/ecs/src/component.js
+++ b/packages/ecs/src/component.js
@@ -1,5 +1,6 @@
 /* eslint-disable guard-for-in, max-classes-per-file, no-restricted-syntax */
 import Schema from './schema';
+import Serializer from './serializer';
 
 class BaseComponent {
 
@@ -15,6 +16,7 @@ class BaseComponent {
 
   constructor(schema) {
     this.schema = schema;
+    this.serializer = new Serializer(schema);
   }
 
   allocate() {
@@ -65,6 +67,13 @@ class BaseComponent {
     }
   }
 
+  set(entity, values) {
+    const instance = this.getUnsafe(entity);
+    for (const i in values) {
+      instance[i] = values[i];
+    }
+  }
+
 }
 
 class FlatComponent extends BaseComponent {
@@ -113,7 +122,7 @@ class FlatComponent extends BaseComponent {
       window.dirty = false;
       window.cursor += this.constructor.width;
     }
-    this.dirty = false;
+    this.setDirty(0, 0);
   }
 
   createMany(entries) {
@@ -175,6 +184,7 @@ class FlatComponent extends BaseComponent {
   }
 
   makeWindowClass() {
+    const Component = this;
     class Window {
 
       cursor = 0;
@@ -192,6 +202,14 @@ class FlatComponent extends BaseComponent {
         }
       }
 
+      toJSON() {
+        const json = {};
+        for (const [i] of Component.schema) {
+          json[i] = this[i];
+        }
+        return json;
+      }
+
     }
     let offset = 0;
     const properties = {};
@@ -200,7 +218,7 @@ class FlatComponent extends BaseComponent {
       `return this.view.get${Schema.viewMethodFromType(type)}(this.cursor + ${offset}, true);`
     );
     const set = (type) => [
-      `this.parent.setDirty(1, this.view.getBigUint64(this.cursor + ${width - 9}, true));`,
+      `this.parent.setDirty(1, Number(this.view.getBigUint64(this.cursor + ${width - 9}, true)));`,
       `this.view.set${Schema.viewMethodFromType(type)}(this.cursor + ${offset}, v, true);`,
       `this.view.setUint8(this.cursor + ${width - 1}, 1, true);`,
     ].join('');
@@ -210,8 +228,8 @@ class FlatComponent extends BaseComponent {
       set: new Function('v', `this.view.setUint8(this.cursor + ${width - 1}, v ? 1 : 0, true);`),
     };
     properties.entity = {
-      get: new Function('', `return this.view.getBigUint64(this.cursor + ${width - 9}, true);`),
-      set: new Function('v', `this.view.setBigUint64(this.cursor + ${width - 9}, v ? 1 : 0, true);`),
+      get: new Function('', `return Number(this.view.getBigUint64(this.cursor + ${width - 9}, true));`),
+      set: new Function('v', `this.view.setBigUint64(this.cursor + ${width - 9}, BigInt(v), true);`),
     };
     for (const [i, spec] of this.schema) {
       const {type} = spec;
@@ -302,6 +320,14 @@ class ArbitraryComponent extends BaseComponent {
         }
       }
 
+      toJSON() {
+        const json = {};
+        for (const [i] of Component.schema) {
+          json[i] = this[i];
+        }
+        return json;
+      }
+
     };
     const properties = {};
     properties.dirty = {
diff --git a/packages/ecs/src/ecs.js b/packages/ecs/src/ecs.js
index 13116da..39c79b0 100644
--- a/packages/ecs/src/ecs.js
+++ b/packages/ecs/src/ecs.js
@@ -1,4 +1,4 @@
-/* eslint-disable guard-for-in, max-classes-per-file, no-restricted-syntax */
+/* eslint-disable guard-for-in, max-classes-per-file, no-continue, no-restricted-syntax */
 
 export default class Ecs {
 
@@ -41,6 +41,10 @@ export default class Ecs {
     return entity;
   }
 
+  createExact(entity, components) {
+    this.createManyExact([entity, components]);
+  }
+
   createMany(count, components) {
     const componentKeys = Object.keys(components);
     const entities = [];
@@ -65,17 +69,102 @@ export default class Ecs {
     return entities;
   }
 
+  createManyExact(entities) {
+    const creating = {};
+    for (let i = 0; i < entities.length; i++) {
+      let components = {};
+      let entity;
+      if (Array.isArray(entities[i])) {
+        [entity, components] = entities[i];
+      }
+      else {
+        entity = entities[i];
+      }
+      if (this.$$entities[entity]) {
+        throw new Error(`can't create existing entity ${entity}`);
+      }
+      const index = this.$$pool.indexOf(entity);
+      if (-1 !== index) {
+        this.$$pool.splice(index, 1);
+      }
+      this.$$entities[entity] = Object.keys(components);
+      for (const j in components) {
+        if (!creating[j]) {
+          creating[j] = [];
+        }
+        creating[j].push([entity, components[j]]);
+      }
+    }
+    for (const i in creating) {
+      this.Components[i].createMany(creating[i]);
+    }
+  }
+
+  decode(view) {
+    let cursor = 0;
+    const count = view.getUint32(cursor, true);
+    if (0 === count) {
+      return;
+    }
+    const keys = Object.keys(this.Components);
+    cursor += 4;
+    const create = [];
+    const update = [];
+    for (let i = 0; i < count; ++i) {
+      const entity = Number(view.getBigUint64(cursor, true));
+      cursor += 8;
+      const components = {};
+      const componentCount = view.getUint16(cursor, true);
+      cursor += 2;
+      for (let j = 0; j < componentCount; ++j) {
+        const id = view.getUint16(cursor, true);
+        const component = keys[id];
+        if (!component) {
+          throw new Error(`can't decode component ${id}`);
+        }
+        components[component] = {};
+        cursor += 2;
+        const instance = this.Components[component];
+        instance.serializer.decode(view, components[component], cursor);
+        cursor += instance.schema.sizeOf(components[component]);
+      }
+      if (this.$$entities[entity]) {
+        update.push([entity, components]);
+      }
+      else {
+        create.push([entity, components]);
+      }
+    }
+    this.createManyExact(create);
+    for (let i = 0; i < update.length; i++) {
+      const [entity, components] = update[i];
+      for (const j in components) {
+        this.Components[j].set(entity, components[j]);
+      }
+    }
+  }
+
+  destroyAll() {
+    this.destroyMany(Object.keys(this.$$entities).map((entity) => parseInt(entity, 10)));
+  }
+
   destroyMany(entities) {
     const map = {};
     for (let i = 0; i < entities.length; i++) {
-      for (let j = 0; j < this.$$entities[entities[i]].length; j++) {
-        const key = this.$$entities[entities[i]][j];
+      const entity = entities[i];
+      if (!this.$$entities[entity]) {
+        throw new Error(`can't destroy non-existent entity ${entity}`);
+      }
+      for (let j = 0; j < this.$$entities[entity].length; j++) {
+        const key = this.$$entities[entity][j];
         if (!map[key]) {
           map[key] = [];
         }
-        map[key].push(entities[i]);
+        map[key].push(entity);
       }
-      this.$$pool.push(entities[i]);
+      this.$$pool.push(entity);
+      delete this.$$entities[entity];
+      this.dirty.delete(entity);
     }
     for (const i in map) {
       this.Components[i].destroyMany(map[i]);
@@ -85,6 +174,54 @@ export default class Ecs {
     }
   }
 
+  encode(entities, view) {
+    if (0 === entities.length) {
+      return;
+    }
+    const keys = Object.keys(this.Components);
+    let cursor = 0;
+    view.setUint32(cursor, entities.length, true);
+    cursor += 4;
+    for (let i = 0; i < entities.length; i++) {
+      let entity;
+      let onlyDirty = false;
+      if (Array.isArray(entities[i])) {
+        [entity, onlyDirty] = entities[i];
+      }
+      else {
+        entity = entities[i];
+      }
+      if (onlyDirty && !this.dirty.has(entity)) {
+        // eslint-disable-next-line no-continue
+        continue;
+      }
+      view.setBigUint64(cursor, BigInt(entity), true);
+      cursor += 8;
+      const components = this.$$entities[entity];
+      view.setUint16(cursor, components.length, true);
+      const componentLengthIndex = cursor;
+      cursor += 2;
+      if (0 === components.length) {
+        continue;
+      }
+      let componentsWritten = 0;
+      for (let i = 0; i < components.length; i++) {
+        const component = components[i];
+        const instance = this.Components[component];
+        if (onlyDirty && !instance.dirty) {
+          continue;
+        }
+        componentsWritten += 1;
+        view.setUint16(cursor, keys.indexOf(component), true);
+        cursor += 2;
+        const source = instance.getUnsafe(entity);
+        instance.serializer.encode(source, view, cursor);
+        cursor += instance.schema.sizeOf(source);
+      }
+      view.setUint16(componentLengthIndex, componentsWritten, true);
+    }
+  }
+
   get(entity, Components = Object.keys(this.Components)) {
     const result = {};
     for (let i = 0; i < Components.length; i++) {
@@ -122,6 +259,38 @@ export default class Ecs {
     }
   }
 
+  sizeOf(entities, onlyDirty) {
+    let size = 0;
+    if (0 === entities.length) {
+      return size;
+    }
+    size += 4;
+    for (let i = 0; i < entities.length; i++) {
+      const entity = entities[i];
+      if (!this.$$entities[entity]) {
+        throw new Error(`can't encode non-existent entity ${entity}`);
+      }
+      if (onlyDirty && !this.dirty.has(entity)) {
+        continue;
+      }
+      size += 8;
+      const components = this.$$entities[entity];
+      if (0 === components.length) {
+        continue;
+      }
+      size += 2;
+      for (let i = 0; i < components.length; i++) {
+        const component = components[i];
+        const instance = this.Components[component];
+        if (onlyDirty && !instance.dirty) {
+          continue;
+        }
+        size += 2 + instance.schema.sizeOf(instance.getUnsafe(entity));
+      }
+    }
+    return size;
+  }
+
   tick(elapsed) {
     for (let i = 0; i < this.$$systems.length; i++) {
       this.$$systems[i].tick(elapsed);
diff --git a/packages/ecs/src/index.js b/packages/ecs/src/index.js
index 0bed1f3..33af058 100644
--- a/packages/ecs/src/index.js
+++ b/packages/ecs/src/index.js
@@ -6,9 +6,26 @@ import Schema from './schema';
 import Serializer from './serializer';
 import System from './system';
 
-const N = 100;
+const N = 1000;
 const warm = 500;
 
+const marks = [];
+
+function mark(label, fn) {
+  marks.push(label);
+  performance.mark(`${label}-before`);
+  fn();
+  performance.mark(`${label}-after`);
+}
+
+function measure() {
+  for (let i = 0; i < marks.length; i++) {
+    const label = marks[i];
+    performance.measure(label, `${label}-before`, `${label}-after`);
+  }
+  console.log(performance.getEntriesByType('measure').map(({duration, name}) => ({duration, name})));
+}
+
 class Position extends Component {
 
   static schema = {
@@ -55,53 +72,42 @@ const createMany = () => {
 for (let i = 0; i < warm; ++i) {
   ecs.destroyMany(createMany());
 }
-performance.mark('create0');
-createMany();
-performance.mark('create1');
+mark('create', createMany);
+
+let buffer, view;
+
+ecs.tick(0.01);
+ecs.tick(0.01);
+if (!view) {
+  buffer = new ArrayBuffer(ecs.sizeOf(Array.from(ecs.dirty.values()), false));
+  view = new DataView(buffer);
+}
+console.log('bytes:', buffer.byteLength);
+const encoding = Array.from(ecs.dirty.values());
+ecs.tickFinalize();
+
+console.log('encoding', encoding.length);
 
 for (let i = 0; i < warm; ++i) {
   ecs.tick(0.01);
+  ecs.encode(encoding, view);
   ecs.tickFinalize();
 }
-performance.mark('tick0');
-ecs.tick(0.01);
-console.log(ecs.dirty.size);
-ecs.tickFinalize();
-console.log(ecs.dirty.size);
-performance.mark('tick1');
-console.log(ecs.$$systems[0].queries.default.count);
 
-performance.measure(`create ${N}`, 'create0', 'create1');
-performance.measure(`tick ${N}`, 'tick0', 'tick1');
+mark('tick', () => ecs.tick(0.01));
+mark('encode', () => ecs.encode(encoding, view));
+mark('finalize', () => ecs.tickFinalize());
 
-const {Position: p} = ecs.get(1);
-console.log({
-  x: p.x,
-  y: p.y,
-  z: p.z,
-  dirty: p.dirty,
-  entity: p.entity,
-});
+ecs.destroyAll();
 
-console.log(performance.getEntriesByType('measure').map(({duration, name}) => ({duration, name})));
+for (let i = 0; i < warm; ++i) {
+  ecs.decode(view);
+  ecs.destroyAll();
+}
 
-// const schema = new Schema({
-//   foo: 'uint8',
-//   bar: 'string',
-// });
+mark('decode', () => ecs.decode(view));
 
-// const serializer = new Serializer(schema);
-// // const source = {foo: 8, bar: 'hello'};
-// // const size = schema.sizeOf(source);
+console.log(JSON.stringify(ecs.get(1)));
 
-// const buffer = new ArrayBuffer(10 + 8);
-// const view = new DataView(buffer);
-// serializer.encode({foo: 8, bar: 'hello'}, view);
-// serializer.encode({foo: 8, bar: 'sup'}, view, 10);
-// console.log(buffer);
-
-// const thing = {};
-// serializer.decode(view, thing);
-// console.log(thing);
-// serializer.decode(view, thing, 10);
-// console.log(thing);
+console.log(N, 'iterations');
+measure();
diff --git a/packages/ecs/src/schema.js b/packages/ecs/src/schema.js
index f68f3e2..c8acd1c 100644
--- a/packages/ecs/src/schema.js
+++ b/packages/ecs/src/schema.js
@@ -11,7 +11,7 @@ export default class Schema {
   constructor(spec) {
     this.spec = this.constructor.normalize(spec);
     for (const i in this.spec) {
-      const {type} = spec[i];
+      const {type} = this.spec[i];
       const size = this.constructor.sizeOfType(type);
       if (0 === size) {
         this.width = 0;
@@ -20,7 +20,7 @@ export default class Schema {
       this.width += size;
     }
     for (const i in this.spec) {
-      this.defaultValues[i] = spec[i].defaultValue;
+      this.defaultValues[i] = this.spec[i].defaultValue;
     }
   }