diff --git a/package.json b/package.json
index 527dfe2..a86162e 100644
--- a/package.json
+++ b/package.json
@@ -5,7 +5,8 @@
   "private": true,
   "scripts": {
     "build": "webpack",
-    "buildProduction": "webpack --mode=production"
+    "buildProduction": "webpack --mode=production",
+    "tsc:check": "tsc --noEmit"
   },
   "author": "Tangent 128",
   "license": "ISC",
diff --git a/src/Ecs/Components.ts b/src/Ecs/Components.ts
index 9e0776f..f0a5a25 100644
--- a/src/Ecs/Components.ts
+++ b/src/Ecs/Components.ts
@@ -1,5 +1,5 @@
 
-import { Data as CoreData, Store } from "./Data";
+import { Data as CoreData, Store, SparseStore } from "./Data";
 import { Layer, SpriteSheet } from "../Applet/Render";
 
 export class Box {
@@ -68,8 +68,8 @@ export class RenderSprite  {
 export class Data extends CoreData {
     location: Store<Location> = [];
     bounds: Store<Polygon> = [];
-    renderBounds: Store<RenderBounds> = {};
-    renderSprite: Store<RenderSprite> = {};
-    collisionSourceClass: Store<CollisionClass> = {};
-    collisionTargetClass: Store<CollisionClass> = {};
+    renderBounds: SparseStore<RenderBounds> = {};
+    renderSprite: SparseStore<RenderSprite> = {};
+    collisionSourceClass: SparseStore<CollisionClass> = {};
+    collisionTargetClass: SparseStore<CollisionClass> = {};
 }
diff --git a/src/Ecs/Data.ts b/src/Ecs/Data.ts
index 1cbb58d..5eaabcf 100644
--- a/src/Ecs/Data.ts
+++ b/src/Ecs/Data.ts
@@ -1,25 +1,26 @@
 
-export interface Component {
-    generation: number;
-}
 
 export type Id = [number, number];
 
-export enum Liveness {
+export const enum Liveness {
     DEAD = 0,
     ALIVE = 1,
     INACTIVE = 2
 }
 
-export interface EntityState extends Component {
+export interface HasGeneration {
+    generation: number;
+}
+export interface EntityState {
     alive: Liveness;
 }
 
-export type Store<T> = (T & Component)[] | Record<number, T & Component>;
+export type Store<T> = (T & HasGeneration)[];
+export type SparseStore<T> = Record<number, T & HasGeneration>;
 export class Data {
-    entity: EntityState[] = [];
+    entity: Store<EntityState> = [];
 
-    [name: string]: Store<{}>;
+    [name: string]: Store<{}> | SparseStore<{}>;
 }
 
 /**
@@ -29,11 +30,8 @@ export class Data {
  * @param state Liveness state, allows creating an inactive entity
  * @returns the new entity's ID and generation
  */
-type StripKeys<T, N> = {
-    [P in keyof T]: P extends N ? never : P
-}[keyof T];
 type Assigner<DATA extends Data> = {
-    [S in keyof DATA]?: Pick<DATA[S][number], StripKeys<DATA[S][number], "generation">>
+    [S in keyof DATA]?: Pick<DATA[S][number], Exclude<keyof DATA[S][number], "generation">>
 };
 export function Create<DATA extends Data>(data: DATA, assign: Assigner<DATA>, state = Liveness.ALIVE): Id {
     const entities = data.entity;
@@ -126,7 +124,7 @@ export function Lookup<
  * @param components names of components to look for
  * @returns the cooresponding components, with unfound ones replaced by nulls
  */
-export function Lookup<DATA extends Data, K extends keyof DATA>(data: DATA, [id, generation]: Id, ...components: K[]): (Component | null)[] {
+export function Lookup<DATA extends Data, K extends keyof DATA>(data: DATA, [id, generation]: Id, ...components: K[]): ({} | null)[] {
     const entity = data.entity[id];
     // inactive entities are fine to lookup, but dead ones are not
     if(entity && entity.generation == generation && entity.alive != Liveness.DEAD) {
@@ -206,11 +204,11 @@ export function Join<
  * Query a Data collection for all Alive entities possessing the named set of Components.
  * @returns an array of tuples containing the matching entity [ID, generation]s & associated Components
  */
-export function Join<DATA extends Data, K extends keyof DATA>(data: DATA, ...components: K[]): [Id, ...Component[]][] {
+export function Join<DATA extends Data, K extends keyof DATA>(data: DATA, ...components: K[]): [Id, ...{}[]][] {
     const entities = data.entity;
-    const stores: Store<{}>[] = components.map(name => data[name]);
+    const stores: (Store<{}>|SparseStore<{}>)[] = components.map(name => data[name]);
 
-    const results: [Id, ...Component[]][] = [];
+    const results: [Id, ...{}[]][] = [];
     const firstStore = stores[0];
     if(Array.isArray(firstStore)) {
         for(let id = 0; id < firstStore.length; id++) {
@@ -223,8 +221,8 @@ export function Join<DATA extends Data, K extends keyof DATA>(data: DATA, ...com
     }
     return results;
 }
-function JoinLoop(id: number, entities: Store<EntityState>, stores: Store<{}>[], results: [Id, ...Component[]][]) {
-    const result: [Id, ...Component[]] = [[id, -1]];
+function JoinLoop(id: number, entities: Store<EntityState>, stores: (Store<{}>|SparseStore<{}>)[], results: [Id, ...{}[]][]) {
+    const result: [Id, ...{}[]] = [[id, -1]];
 
     let generation = -1;
     for (const store of stores) {
diff --git a/src/Ecs/test.ts b/src/Ecs/test.ts
index b11aa1d..69e8160 100644
--- a/src/Ecs/test.ts
+++ b/src/Ecs/test.ts
@@ -4,15 +4,15 @@ import { Loop } from "../Applet/Loop";
 import { Layer, DrawSet } from "../Applet/Render";
 import { Data, Location, Polygon, RenderBounds, CollisionClass } from "./Components";
 import { FindCollisions } from "./Collision";
-import { Component, Join, Liveness, Remove, Create, Lookup } from "./Data";
+import { Join, Liveness, Remove, Create, Lookup, Store, SparseStore } from "./Data";
 import { DumbMotion } from "./Location";
 import { RunRenderBounds } from "./Renderers";
 
-interface Apple extends Component {}
-interface Banana extends Component {
+interface Apple {}
+interface Banana {
     peeled: boolean
 }
-interface Carrot extends Component {
+interface Carrot {
     cronch: number
 }
 
@@ -25,7 +25,7 @@ class TestData extends Data {
         {generation: 5, alive: Liveness.INACTIVE},
         {generation: 5, alive: Liveness.ALIVE},
     ];
-    apple: Apple[] = [
+    apple: Store<Apple> = [
         {generation: 5},
         {generation: 5},
         {generation: -1},
@@ -33,11 +33,11 @@ class TestData extends Data {
         {generation: 5},
         {generation: 5},
     ];
-    banana: Record<number, Banana> = {
+    banana: SparseStore<Banana> = {
         3: {generation: 5, peeled: false},
         4: {generation: 5, peeled: true},
     };
-    carrot: Record<number, Carrot> = {
+    carrot: SparseStore<Carrot> = {
         0: {generation: 5, cronch: 1},
         1: {generation: 5, cronch: 1},
         2: {generation: 4, cronch: 10},
diff --git a/src/Game/GameComponents.ts b/src/Game/GameComponents.ts
index 538dff5..2811c5b 100644
--- a/src/Game/GameComponents.ts
+++ b/src/Game/GameComponents.ts
@@ -1,5 +1,5 @@
 import { Layer, DrawSet } from "../Applet/Render";
-import { Store } from "../Ecs/Data";
+import { SparseStore } from "../Ecs/Data";
 import { Data as EcsData } from "../Ecs/Components";
 
 export enum GamePhase {
@@ -54,11 +54,11 @@ export class World {
 }
 
 export class Data extends EcsData {
-    boss: Store<Boss> = {};
-    bullet: Store<Bullet> = {};
-    hp: Store<Hp> = {};
-    lifetime: Store<Lifetime> = {};
-    message: Store<Message> = {};
+    boss: SparseStore<Boss> = {};
+    bullet: SparseStore<Bullet> = {};
+    hp: SparseStore<Hp> = {};
+    lifetime: SparseStore<Lifetime> = {};
+    message: SparseStore<Message> = {};
 }
 
 export enum Teams {