diff --git a/src/core/game.ts b/src/core/game.ts
index 5d07ef5..c8a9945 100644
--- a/src/core/game.ts
+++ b/src/core/game.ts
@@ -58,7 +58,6 @@ export function createGameContextFromModule<TState extends Record<string, unknow
 export function createGameCommandRegistry<TState extends Record<string, unknown> = {} >(): CommandRegistry<IGameContext<TState>> {
     return createCommandRegistry<IGameContext<TState>>();
 }
-</TState>
 
 export function createGameCommand<TState extends Record<string, unknown> = {} , TResult = unknown>(
     schema: CommandSchema | string,
diff --git a/src/core/part.ts b/src/core/part.ts
index 5638577..16a5de5 100644
--- a/src/core/part.ts
+++ b/src/core/part.ts
@@ -4,9 +4,11 @@ import {RNG} from "../utils/rng";
 
 export type Part = {
   id: string;
-  sides: number;
+
+  sides?: number;
+  side?: number;
+
   alignments?: string[];
-  side: number;
   alignment?: string;
   region: Entity<Region>;
   position: number[];
@@ -14,18 +16,21 @@ export type Part = {
 
 export function flip(part: Entity<Part>) {
   part.produce(draft => {
-    draft.side = (draft.side + 1) % draft.sides;
+    if(!draft.sides)return;
+    draft.side = ((draft.side||0) + 1) % draft.sides;
   });
 }
 
 export function flipTo(part: Entity<Part>, side: number) {
   part.produce(draft => {
+    if(!draft.sides || side >= draft.sides)return;
     draft.side = side;
   });
 }
 
 export function roll(part: Entity<Part>, rng: RNG) {
   part.produce(draft => {
+    if(!draft.sides)return;
     draft.side = rng.nextInt(draft.sides);
   });
 }
diff --git a/src/samples/tic-tac-toe.ts b/src/samples/tic-tac-toe.ts
index 54f13e8..20174d0 100644
--- a/src/samples/tic-tac-toe.ts
+++ b/src/samples/tic-tac-toe.ts
@@ -63,8 +63,6 @@ export function placePiece(host: IGameContext<TicTacToeState>, row: number, col:
     const board = getBoardRegion(host);
     const piece: Part = {
         id: `piece-${moveCount}`,
-        sides: 1,
-        side: 0,
         region: board,
         position: [row, col],
     };